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Digitized by the Internet Archive 
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BY THE SAME AUTHOR 


ELEMENTARY ZOOLOGY 
Pp. xv-+492, 172 figs., 12m0, 1901, 
$1.20 

FIRST LESSONS IN ZOOLOGY 


Pp. x-+363, 257 figs., 12m0, 1903, |. 


$1.15 

AMERICAN INSECTS 
Pp. viit+671, 812 figs., 11 colored | 
plates, 8vo, 1905 (American Nature 
Series, Group 1), $5.00. Students’ } 
edition, $4.00 


HENRY HOLT AND COMPANY 
PUBLISHERS New York 





DARWINISM TO-DAY 


A DISCUSSION OF PRESENT-DAY SCIENTIFIC CRITICISM 
OF THE DARWINIAN SELECTION THEORIES, TO- 
GETHER WITH A BRIEF ACCOUNT OF THE 
PRINCIPAL OTHER PROPOSED AUXIL- 

IARY AND ALTERNATIVE THEO- 

RIES OF SPECIES-FORMING 


BY 


VERNON L. KELLOGG 


PROFESSOR IN LELAND STANFORD, JR., UNIVERSITY 


LIBRARY OF PRINCETON 






LOGICAL SEMINARY 





THEO 





NEW YORK 
HENRY HOLT AND COMPANY 
1907 


COPYRIGHT, 1907, 
BY 
HENRY HOLT AND COMPANY 





Published August, 1907 


THE QUINN & BODEN CO. PRESS 
RAHWAY, N. J. 


BNE AG ie 


Tus book is written for the sake of presenting simply and 
concisely to students of biology and to general readers the 
present-day standing of Darwinism in biological science, and 
to outline for them the various auxiliary and alternative 
theories of species-forming which have been proposed to aid 
or to replace the selection theories. 

Our actual knowledge of the factors and mechanism of 
organic evolution and our hypotheses and theories which 
serve to fill in the present gaps in this knowledge have been 
greatly added to and modified in the last few years. Much 
that the general reader includes in his conception of organic 
evolution, based on his reading of Darwin and Wallace and 
Spencer, has been materially modified and some of it proved 
untenable by modern investigation; while much which had 
no place in this earlier general understanding of evolutionary 
method and process may now be confidently added to it. The 
present time is one of unprecedented activity and fertility 
both in the discovery of facts and in attempts to perceive 
their significance in relation to the great problems of bio- 
nomics. Both destructive criticism of old, and synthesis of 
new hypotheses and theories, are being so energetically car- 
ried forward that the scientific layman and educated reader, 
if he stand but ever so little outside of the actual working 
ranks of biology, is likely to lose his orientation as to the 
trend of evolutionary advance. Precisely at the present mo- 
ment is this modification of the general point of view and 
attitude of philosophical biologists unusually important and 
far-reaching in its relation to certain long-held general con- 
ceptions of biology and evolution. This modification of the 
general trend of evolutionary thought must also necessarily 


ili 


iv PREFACE, 


strongly affect our conceptions of the underlying principles 
of such correlated sciences as sociology, pedagogy, etc. It 
is, then, as a means of orientation in evolutionary matters for 
the general reader and for the unspecialised but interested 
student of science that this book is prepared. 

That it may not be without some special usefulness to 
more advanced students and biological workers there are 
added, in appendices to the chapters, special notes (referred 
to in the text by small super-numbers) in which are given 
numerous exact references to general or special books or 
papers, and accounts, in more or less detail, of particular 
observations, experiments, or theoretical discussions, as well 
as references to extended bibliographic lists of the subjects 
under treatment. These notes will enable students, or others 
interested, to look up the original sources of our knowledge 
of the subjects of the various chapters, and to find more 
detailed general or special discussions of them than can be 
given in this book. These notes also enable the author to 
introduce into the book some details of his own observations 
and experiments touching various evolutionary subjects. 


a A se 


STANFORD UNIVERSITY, /“7é, 1907. 


CONTENTS. 


CHAPRTEREL, ’ 
PAGE 
INTRODUCTORY: 7 ‘THE, “DEATH - BED OR} “DARs 
WINISM” A ‘ : : : I 
Modern pote in Biotest maith . Darwinism not 
synonymous with evolution, 3. Present-day anti-Darwin- 
ism, 4. Intemperate anti-Darwinism, 6. Outline of this 
book, 7. 
APPENDIX: Dennert’s intemperate attack on Darwinism, 
7, An anti-evolution university biologist, 8. Friedmann’s 
theory to replace evolution with divergence, 8. 


CHARLERULL 


DARWINISM AND EVOLUTION DEFINED AND 
DISTINGUISHED : : eek O 

Animal and plant kinds sarang: in one ee fires ae 
10. The theory of descent defined, 11. The theory of 
descent given validity by Darwin’s explanation of the 
cause of it, 12. Darwinism defined and analysed into its 
fundamental assumptions and facts, 13. Sources of scien- 
tific evidence for the theory of descent, 17. Relation of 
theology, philosophy, pedagogy, and sociology to the 
theory of descent, 20. 

APPENDIX: Accounts of history of the descent theory, 
22. Books giving the evidences for descent, 23. Dis- 
cussions of the relation of descent and theology, 23. 
Discussions of the relations of biology and philosophy, 24. 
Biology and sociology, 24. 


CHARTER SLL, 


DARWINISM ATTACKED _. ; : ; : ee 
The attack of the theologians, os. The present-day 
attack of the scientific men, 25. Some of the principal 
objections to natural selection summarised, 30. Darwinian 
or fluctuating variations too small to serve as ‘‘handles” 


Vv 


vi 


CONTENTS: 


for natural selection, 36. Many specific differences are 
indifferent, z. ¢., not adaptive, 38. The extinguishing of 
the extreme variations by interbreeding, 44. The im- 
probability of the occurrence of the right variations at the 
right time, 45. The difficulty of explaining the production 
by natural selection of specialisations useful only in highly 
complex condition, 49. The objection based on the over- 
development of specialisations, 53. The objection based 
on insufficient time, 54. The objection that natural selec- 
tion tends to preserve the type rather than the variants, 
and hence opposes change, 56. 

ApPENDIx: Books and papers on variation, 57. Cases of 
marked variation in parthenogenetic animals, 58. Varia- 
tion according to the law of probabilities, 59. Quetelet, 
the discoverer of variation according to the laws of chance, 
61. Example of trivial variations, 62. Ndageli’s seven 


objections to species-forming by selection, 62. Wolff’s 


attack on the selectionists’ assumption of the appearance 
at the right time of the needed variation, 64. Example of 
non-correlated variability in bilaterally repeated organs, 
65. Henslow’s antagonism to selection as an explainer of 
floral correlations, 67. Wolff’s objection to the necessary 
assumption of identical and coincident variation in re- 
peated structures, as feathers, scales, etc., 67. Example 
of mal-adaption in the egg-laying habit of Plryganzdia 
caltfornica, 68—Pieper’s antagonism to the selection ex- 
planation of colour and pattern in insects, 69. 


CHAR TE Rahs 


DARWINISM ATTACKED (Continued) Na our 


Objection to the exclusively linear or quantitative Ghar 
acter of the fluctuating or Darwinian variations, 70. 
Galton’s law of regression, 71. Selection may produce 
evolution (continuous change) but not species (discontinu- 
ous series), 73. Pfeffer’s objection based on the slowness 
of species transformation, 75. The difficulty of explaining 
the sterility of species by selection, 76. Selection cannot 
explain extreme or complete degeneration of useless parts, 
77. Objections to the assumed rigour of the struggle for 
existence and to the actuality of intra-specific or personal 
selection, 79. Indiscriminate extermination due to the 
fortune of position and time, 80. The necessity of sexual 


PAGE 


7° 


CONTENTS. vil 


PAGE 
selection, a discredited theory, for the support of the 
natural selection theory, 85. Natural selection rests on an 
unwarranted assumption of its homology with artificial 
selection, 86. Many biologists find natural selection 
unable to account for known biologic conditions, 89. Sig- 
nificance of the concessions of Darwinians, go. Kor- 
schinsky’s extreme anti-Darwinian doctrine, 91. Delage’s 
“true rdle of selection,” 93. Morgan’s rejection of natural 
selection as a species-forming factor, 93. 

APPENDIX: Galton’s statement of the law of regression, 
97. Wolff's criticism of panmixia, 98. Example of inef- 
fective panmixia, 100. Example of progressive degenera- 
tion inexplicable by natural selection, 100. Wolff's 
discussion of the selection coefficient, 1or1. Example of 
non-selection of trivial differences, 103. References to 
books and papers on plant breeding, 105, 


Ole Fe TI EY Ce 


DARWINISM ATTACKED (Continued): THE THEORY 
OF SEXUAL SELECTION : : : - : -. 106 
Secondary sexual differences or characters, 107. Classi- 
fication of secondary sexual characters, 107. Useless and 
harmful characters not explicable by natural selection, 
110. Theory of sexual selection to account for them: the 
theory defined, 111. Darwin’s assumptions as basis of the 
theory of sexual selection, 112. Difficulties in the way ofa 
general application of the theory, 113, The theory appli- 
cable only to species in which males are more numerous 
than females, 113. The passivity of females, 114. Males 
of species in which no real pairing occurs also show strik- 
ing secondary sexual characters, 114. Necessity of 
assuming unproved esthetic development among lower 
animals, 114. Few recorded cases of observed choosing 
by female, 115. Difficult to assume utility for many 
secondary sexual characters, 115. Stolzmann’s case of the 
Andean humming-birds, 116. Howexplain the beginnings. 
of secondary sexual characters, 117. How explain orna- 
mental characters appearing in both males and females, 
118. Morgan’s objections to sexual selection theory, 118. 
Experimental evidence touching the theory is against it, 
120. Mayer’s experiments with Promethea and Porthetria 
moths, 121. Douglass’s and Diirigen’s observations on 


Vill 


CONTENTS: 


lizards, 123. Substitutionary theories of the origin of 
secondary sexual characters, 124. 

APPENDIX: References to books and papers discussing 
sexual selection, 125. Wolff’s critical exposition of weak- 
nesses in sexual selection, 126. 


CHALLE R aT. 


DARWINISM DEFENDED 


Position of the defenders of Darwinient nae Reaction 
against the too. speculative positions of Haeckel and 
Weismann, 130. ‘‘Haeckelismus,” 130. Weismannism, 
131. Struggle between Neo-Darwinians and Neo-La- 
marckians, 133. Concessions of the Neo-Darwinians, 134. 
Answer to objection concerning the too slight character of 
fluctuating or Darwinian variations to serve as handles for 
natural selection, 138. Answer to the objection concern- 
ing the linear and quantitative character of Darwinian 
variation, 139. Answer to the objection that selection can- 
not produce many-branched descent, 142. Answer to the 
statement that selection can produce continuous change 
or evolution, but not species, 143. Answer to the objec- 
tion concerning the production by selection of co-adaptive 
and highly complex specialisations, 144. Answer to the 
objection concerning the over-development of specialisa- 
tions, 146. Discussion of the difficulty that natural selec- 
tion has with structural degeneration, 146. The Darwinian 
answer to the expressions of doubt about the rigour of 
selection, 148. Answer to the objections to the sexual 
selection theory, 148. Discussion of the objection to the 
derivation of evidence for natural selection from the facts 
of artificial selection, 150. Tayler’s general defence, 153. 

APPENDIX: Weldon’s experiments on Carcinus, 158. 
Tayler’s explanation of degeneration by natural selection, 
162. Plate’s explanation of character fixity in domestic 
animals, 163. 


CHARTER Vil, 


DARWINISM DEFENDED (Continued): PLATE’S CON- 


CILIATORY DEFENCE 

Plate, a fair-minded Darwinian Ateieatoa tone Waanere 
to the objection based on the slight character and inutility 
of Darwinian variations, 165. Many slight differences at 


PAGE 


129 


164 


CONTENTS. 1X 


PAGE 
first glance apparently indifferent in character found on 


more careful inspection to be of advantage, 166. Slight 
characters aided by co-related differences, 167. The prin- 
ciple of the change of function, 168. Characters of in- 
different value under one condition of environment, 
suddenly made important by a change in life-conditions, 
169. Organs of universal character which can become 
modified in various directions, 169. Lamarckian factors 
called to the aid of Darwinism, 170. Answers to the 
objection based on the improbability of the appearance of 
the right variations at the right time for the progressive 
perfecting or development of an organ, 170. Selection 
directs itself according to variation, not variation accord- 
ing to any assumed needs of selection, 171. Selection 
works with plural variations, not single ones, 172, The 
same selective value can often be attained through combi- 
nations of various peculiarities and the same effect 
reached by various means, 172. The element of chance 
not peculiar to the Darwinian explanation of co-adap- 
tations, 175. Answers to the objection based on the 
assumed improbability that during the course of the 
development of a complex organ or whole body-part, or 
during the perfecting of a changing adaptation the 
numerous necessary adaptations will occur in such a suc- 
cessive series as to make possible any harmonious correla- 
tion of the various single variations, 176. Plate’s reliance 
on the Lamarckian factor of the inheritance of characters 
acquired through use, disuse, and other functional stimuli, 
178. The attainment of selective value by various means, 
178. Weismann’s theory of germinal selection unaccept- 
able, 180. Weismann’s principle of amphimixis of great 
importance, 180. The necessity of concessions admitted 
181. The necessity of invoking auxiliary or aiding prin- 
ciples to support the natural selection theory, 182. 
APPENDIX: Conn’s discussion of selective value, 182. 
References to papers on correlation, 184. Cope’s proof 
that natural selection cannot originate new characters, 185. 


CHAPTER VIII. 


OTHER THEORIES OF SPECIES-FORMING: THEO- 
RIES AUXILIARY TO SELECTION . ‘ eo] 

The presentation of theories to aid the selection theories 

or others to replace them really a continuation of-the 


x GON TENDS: 


PAGE 
defence of, and attack on, Darwinism, 187. The Weis- 


mannian theories, 188. Panmixia, 190. The theory of 
germinal selection, 193. The physical and chemical 
structure of protoplasm, 194. Objections to the theory 
of germinal selection, 200. Roux’s theory of intra-selec- 
tion, or the battle of the parts, 201. Objections to Roux’s 
theory, 203. The theory of organic selection, or ortho- 
plasy, 208. 

APPENDIX: List of Weismann’s evolution papers, 212. 
Theories of ultimate protoplasmic structure, 214. Encase- 
ment theory, 215. Micromeric theories, 215. Buffon’s 
theory, 216. Spencer's. (theory, 12175) Darwin sietieory, 
218. Ndageli’s theory, 219. De Vries’s theory, 220. Hat- 
schek’s theory, 222. Delage’scriticisms, 224. Le Dantec’s 
criticisms, 224. Verworn’s biogen hypothesis, 225. De- 
lage’s machine theory, 225. Le Dantec’s theory of 
chemism, 225. Neo-vitalism, 226. Morgan’s criticism of 
Weismann’s method of argument, 229. References to 
discussions of orthoplasy, 229. 


CHAT FRA: 


OTHER THEORIES OF SPECIES-FORMING (Continued): 
THEORIES AUXILIARY TO SELECTION (Continued) 232 

Isolation theories, 232. Wagner’s ‘‘Separations-theorie,” 
234. Jordan’s upholding of the importance in species- 
forming of geographic isolation, 237. Biologic and sexual 
isolation, or physiological selection, 243. Gulick’s work 
and conclusions, 249. 

APPENDIX: References to discussions of ore tone 253. 
Haacke’s summary of Wagner's theory, 253. Grinnell’s 
studies of geographic differences in the chickadee, 255. 
Further references to discussions of isolation, 261. 


GHARPLIE REX, 


OTHER THEORIES OF SPECIES-FORMING (Con- 
tznued). THEORIES ALTERNATIVE TO SELEC- 
TION ; : 262 

Three general eons of theres proposed to panieee fab 
selection theories as explanations of species-forming and 
evolution, 262. The Lamarckian theory, 262. Objections 
to the Lamarckian factors, especially that of the inheritance 


CONTENTS: xl 


PAGE 
of acquired characters, 266. Great use could be made of 


the Lamarckian factors in explaining evolution phenomena 
if these factors could be given validity, 271. Orthogenesis 
and determinate variation, pointing toward orthogenesis, 
271. Nageli’s theory of orthogenesis, 277. Eimer’s ortho- 
genetic theory, 282. Cope’s theory of bathmism and 
kinetogenesis, 285. Jaeckel’s theory of metakinesis, 289. 

APPENDIX: Referencesto Lamarck’s writings, 290. Brown- 
Séquard’s experiments on guinea pigs, 290. Hyatt’s 
studies of Planordzs, 295.. Fischer’s experiments with 
butterflies, 296. Experiments with silkworms, 298. Ref- 
erences to books and papers on inheritance of acquired 
characters, 305. Redfield’s position, 305. Montgomery’s 
explanation of inheritance of variation, 306. Scientific 
aspects of Burbank’s work, 310. Orthogenetic variation 
in paleontology, 319. A case of apparent determinate 
variation, 319. Pfeffer’s theory of orthogenesis, 320. 
Eimer’s theory of orthogenesis, 321. Apparent determi- 
nate evolution, 322. Snodgrass’s observances on bills of 
Galapagos birds, 323. Cope’s belief in orthogenetic evolu- 
tion, 323. Whitman’s belief in determinate variation, 325. 
Cunningham and orthogenesis, 326. 


COAPTER XS, 


OTHER THEORIES OF SPECIES-FORMING (Con- 
tinued); THEORIES ALTERNATIVE TO SELEC- 
TION (Continued) : : : Wee ey 

Heterogenesis or the wept tHenry 327. firoentutes 
tions of heterogenesis theories by von Kolliker, Dall, 
Galton, and Emery, 330. Korschinsky’s heterogenesis 
theory, 333. [De Vries’s mutations theory, 337. Present 
status of de Vries’s theory, 348. Alternative theories to 
explain secondary sexual characters, 352. 

APPENDIX: Mendel and his work, 356. References to 
recent work on Mendelism, 357. Darwin's examples of 
race origin from sports, 357. A recent example of race 
origin from a sport in cattle, 358. Galton’s discussion of 
specific stability, 360. References to discussions by de 
Vries of species-forming, 362. American opinions of the 
mutations theory, 362. Davenport’s example of species 
origin by slight continuous change, 367. Merriam’s criti- 
cism of the mutations theory, 367. Plate’s criticism of the 


Xii 


CONTENTS. 


mutations theory, 368. References to theories explaining 
secondary sexual characters, 373. 


CHARTER XLT, 


DARWINISM’S PRESENT STANDING 


Natural selection the final control in evolution, but not 
a sufficient explanation of species-forming, 374. Weak- 
nesses of the substitutionary theories, 375. The unknown 
factors of evolution, 377. Prime needs of evolution study; 
first, the intensive study, statistical and experimental, of 
variability, 378. Second, the means of cumulating varia- 
bility along definite lines, 379. Third, the investigation of 
adaptation, 380. A suggested argument for a belief in the 
transference of ontogenic changes into phylogeny, 382. A 
suggested automatic causal factor of variability, purposive 
but not purposeful, 384. Our present ignorance and the 
call to work, 387. 

APPENDIX: Wigand’s criticism of the selection theories, 
387. Lankester’s upholding of Darwinism, 389. De Vries’s 
discussion of species-forming by selection, 389. Delage’s 
estimate of selection, 390. Osborn’s championship of the 
unknown factors of evolution, 391. Klebs’s conclusions 
from experiments on plants, 392. Friedlander’s discussion 
of adaptation, 392. Loeb’s attitude toward the problem of 
species-forming, 393. 


INDEX ater YM a) cs eaile Sia) Ake Sehnge, Malo hs aca aan a 


PAGE 


374 


397 


DARWINISM TO-DAY 





DARWINISM TO-DAY. 


CHARLERS | 


PNURODUG TORY Piet DAE Binh) Gi 
DARWINISM.” 


“Vom STERBELAGER DES DARwinisMus!” This is the 
title of a recent pamphlet * lying before me. But ever since 
there has been Darwinism there have been occasional death- 
beds of Darwinism on title pages of pamphlets, addresses, 
and sermons. Much more worth consideration than any 
clerical pamphlets or dissertations, under this title, by frisch- 
gebackenen German doctors of philosophy—the title alone 
proving prejudice or lack of judgment or of knowledge— 
are the numerous books and papers which, with less sensa- 
tional headlines but infinitely more important contents, are 
“appearing now in such numbers and from such a variety of 
reputable sources as to reveal the existence among biologists 
and philosophers of a widespread belief in the marked . 
weakening, at least, if not serious indisposition, of Darwin- 
ism. A few of these books and papers from scientific sources 
even suggest that their writers see shadows of a death-bed. 

The present extraordinary activity in biology is two- 
phased; there is going on a’ most careful re-examination or 

Modern activ. Scrutiny of the theories connected with organic 
ity in biologic evolution, resulting in much destructive criti- 
ahh cism of certain long-cherished and widely held 
beliefs, and at the same time there are being developed and 
almost feverishly driven forward certain fascinating and 
fundamentally important ‘new lines, employing new methods, 


2 DARWINISM TO-DAY. 


of biological investigation. Conspicuous among these new 
kinds of work are the statistical or quantitative study of 
variations and that most alluring work variously called 
developmental mechanics, experimental morphology, ex- 
perimental physiology of development, or, most suitably of 
all because most comprehensively, experimental biology.’ 
This work includes the controlled modification of conditions 
attending development and behaviour, and the pedigreed 
breeding of pure and hybrid generations. Now this combina- 
tion of destructive critical activity and active constructive ex- 
perimental investigation has plainly resulted, or is resulting, 
in the distinct weakening or modifying of certain familiar 
and long-entrenched theories concerning the causative factors 
and the mechanism of organic evolution.’ Most conspicuous 
among these theories now in the white light of scientific 
scrutiny are those established by Darwin, and known, col- 
lectively, to biologists, as Darwinism. 

To too many general readers Darwinism is synonymous 
with organic evolution or the theory of descent.’ The word 
is not to be so used or considered. ’ Darwinism, 
primarily, is a most ingenious, most plausible, 
and, according to one’s belief, most effective or 
most inadequate, causo-mechanical explanation of adaptation 
and species-transforming. It is that factor which, ever since 
its proposal by Darwin in 1859, has been held by a majority 
of biologists to be the chief working agent in the descent, 
that is, the origin, of species. However worthy Darwin is of 
having his name applied directly to the great theory of 
descent—for it was only by Darwin’s aid that this theory, 
conceived and more or less clearly announced by numerous 
pre-Darwinian naturalists and philosophers, came to general 
and nearly immediate acceptance—the fact is that the name 
\ Darwinism has been pretty consistently applied by biologists 
only to those theories practically original with Darwin which 
offer a mechanical explanation of the accepted fact of 


What Dar- 
winism is, 


INTRODUCTORY: “DEATH-BED OF DARWINISM.” 3 


descent. ‘Of these Darwinian theories the primary and all- 
important one is that of natural selection.’ Included with 
this in Darwinism are the now nearly wholly discredited 
theories of sexual selection and of the pangenesis of gem- 
mules. It may also be fairly said that the theory of the 
descent of man from the lower animals should be included in 
Darwinism.” For Darwin was practically the first naturalist 
bold enough to admit the logical and obvious consequences 
of the general acceptance of the theory of descent, and to 
include man in the general chain of descending, or ascend- 
ing, organisms. So that the popular notion that Darwinism 
is in some way the right word to apply to the doctrine that 
man has come from the monkeys is rather nearer right than 
wrong. But biologists do not recognise the descent of man 
as a special phase of Darwinism, but rather of the whole 
theory of descent, or organic evolution. 
‘Darwinism, then, is not synonymous with organic evolu- 
tion, nor with the theory of descent (which two phases are 
f, used by the biologist practically synonymously ). 
Darwinism 
not synonymous Lherefore when one reads of the “death-bed of 
with evolution. Parwinism,” it is not of the death-bed of or- 
ganic evolution or of the theory of descent that one is read- 
ing. While many reputable biologists to-day strongly doubt 
the commonly reputed effectiveness of the Darwinian selec- 
tion factors to explain descent—some, indeed, holding them 
to be of absolutely no species-forming value—practically 
no naturalists ° of position and recognised attainment doubt 
the theory of descent.*” Organic evolution, that is, the 
descent of species, is looked on by biologists to be as proved 
a part of their science as gravitation is in the science of 
physics or chemical affinity in that of chemistry. Doubts 
of Darwinism are not, then, doubts, of organic evolution. 
Darwinism might indeed be on its death-bed without shaking 
in any considerable degree the confidence of biologists and 
natural philosophers in the theory of descent. | 


4 DARWINISM TO-DAY. 


‘But the educated reader, the scientific layman, the thinker 
and worker in any line of sociologic, philosophic, or even 
theologic activity is bound to be disturbed and 
Present-day 

anti-Darwin- | unsettled by rumours from the camp of pro- 
pins fessional biologists of any weakness or mortal 
illness of Darwinism. We have only just got ourselves and 
our conceptions of nature, of sociology and philosophy, well 
oriented and adjusted with regard to Darwinism.’ And for 
relentless hands now to come and clutch away our founda- 
tions is simply intolerable. Zum Teufel with these German 
professors! \For it is precisely the German biologists who 
are most active in this undermining of the Darwinian 
‘theories. But there are others with them; Holland, Russia, 
Italy, France, and our own country all contribute their 
quota of disturbing questions and declarations of protest 
and revolt.» The English seem mostly inclined to uphold 
the glory of their illustrious countryman.~ But there are 
rebels even there. Altogether it may be stated with full 
regard to facts that a major part of the current published 
output of general biological discussions, theoretical treatises, 
addresses, and brochures dealing with the great evolutionary 
problems, is distinctly anti-Darwinian in character. ° This 
major part of the public discussion of the status of evolution 
and its causes, its factors and mechanism, by working 
biologists and thinking natural philosophers, reveals a 
lack of belief in the effectiveness or capacity of the natural 
‘selection theory to serve as a sufficient causo-mechanical 
explanation of species-forming and evolution. Nor is this 
preponderance of anti-Darwinian expression in current 


biological literature to be wholly or even chiefly attributed 


to a dignified silence on the part of the believers in selection. 
Answers and defences have appeared and are appearing. 
But in practically all these defences two characteristics are 
to be noted, namely, a tendency to propose supporting 
hypotheses or theories, and a tendency to make certain 


An aaa 


INTRODUCTORY: *“DEATH-BED. OF DARWINISM.” = 5 


distinct concessions to the beleaguering party. eas fair 
truth is that the Darwinian selection theories, c¢onsidered 
with regard to their claimed capacity to be an independently 
sufficient mechanical explanation of descent, stand to-day 
seriously discredited in the biological world. ‘On the other 
hand, it is also fair truth to say that no replacing hypothesis 
or theory of species-forming has been offered by the oppo- 
nents of selection which has met with any general or even 
considerable acceptance by naturalists.” Mutations seem to 
be too few and far between; for orthogenesis we can dis- 
cover no satisfactory mechanism; and the same is true for 
the Lamarckian theories of modification by the cumulation,. 
through inheritance, of acquired or ontogenic characters. 
Kurg und gut, we are immensely unsettled. 

Now but little of this philosophic turmoil and wordy 
strife has found its way as yet into current American litera- 
ture. Our bookshop windows offer no display, as in Ger- 
many, of volumes and pamphlets on the newer evolutionary 
study ; our serious-minded quarterlies, if we have any, and. 
our critical monthlies and weeklies contain no debates or 
discussions over “das Sterbelager des Darwinismus.” Our 
popular magazines keep to the safe and pleasant task of 
telling sweetly of the joys of making Nature’s acquaintance: 
through field-glasses and the attuned ear. But just as cer- 
tainly as the many material things “made in Germany” have 
found their way to us so will come soon the echoes and 
phrases of the present intellectual activity in evolutionary 
affairs, an activity bound to continue as long as the new 
lines of biological investigation continue their amazing out- 
put of new facts to serve as the bases for new critical attacks 
on the old notions and for the upbuilding of new hypotheses. 
If now the first of these echoes to come across the water 
to us prove to be, as wholly likely, those from the more vio- 
lent and louder debaters, they may lead to an undue dismay 
and panic on our part. Things are really in no such desper- 


6 DARWINISM TO-DAY. 


ate way with Darwinism as the polemic vigour of the Ger- 
man and French anti-Darwinians leads them to suggest. 
Says one of them: “Darwinism now belongs to history, 

Meera like that other curiosity of our century, the 
anti-Darwin- © Hegelian philosophy; both are variations on the 
ee theme: how one manages to lead a whole gen- 
eration by the nose.” The same writer also speaks of “the 
- softening of the brain of the Darwinians.”’ Another one,” in 
similarly relegating Darwinism to the past, takes much pleas- 
ure in explaining that “we [anti-Darwinians] are now stand- 
ing by the death-bed of Darwinism, and making ready to 
send the friends of the patient a little money to insure a 
decent burial of the remains.”” No less intemperate and in- 
decent is Wolff’s ' reference to the “episode of Darwinism”’ 
and his suggestion that our attitude toward Darwin should 
be “as if he had never existed.” Such absurdity of ex- 
pression might pass unnoticed in the mouth of a violent 
non-scientific debater—let us say an indignant theologian 
of Darwin’s own days—but in the mouth of a biologist of 
recognised achievement, of thorough scientific training and 
unusually keen mind—for this expression came from just 
such a man—it can only be referred to as a deplorable ~ 
example of those things that make the judicious to grieve. 
Such violence blunts or breaks one’s own weapons. 

While I have said that the coming across the water of 
the more vigorous anti-Darwinian utterances might cause 
some dismay and panic in the ranks of the educated reader— 
really unnecessary panic, as I hope to point out—it will 
doubtless occur to some of my readers to say that this fear 
of panic is unwarranted. If the first phrases to come are 
as injudicious and intemperate, hence as unconvincing, as 
those just cited, the whole anti-Darwinian movement will 
be discredited and given no attention. Which, I hasten to 
reply, will be as much of a mistake as panic would be. 
There is something very seriously to be heeded in the 


INTRODUCTORY: “DEATH-BED OF DARWINISM.” 7 


chorus of criticism and protest, and wholly to stop one’s 
ears to these criticisms is to refuse enlightenment and to 
show prejudice. I have thought it, therefore, worth while 
to try to anticipate the coming of fragmentary 
and disturbing extracts from the rapidly in- 
creasing mass of recent anti-Darwinian litera- 
ture by presenting in this book a summary account not alone 
of these modern criticisms, but of the answers to them by the 
steadfast Darwinians, and of the concessions and supporting 
hypotheses which the supporters of both sides have been led 
to offer during the debates. I shall try to give a fair state- 
ment of the recent attacks on, and the defence and present 
scientific standing of, the familiar Darwinian theories, and 
to give also concise expositions, with some critical comment, 
of the more important new, or newly remodelled alternative 
and auxiliary theories of species-forming and descent, such 
as heterogenesis, orthogenesis, isolation, etc., and an esti- 
mate of their degree of acceptance by naturalists. 


Outline of 
this book. 


APPENDIX. 


*Dennert, E., “Vom Sterbelager des Darwinismus,” Stuttgart, 
1903. An intemperate and unconvincing but interesting brief against 

Dennert’sin- the Darwinian factors, 7. e., the selection theories, in 
temperate attack evolution. Author fully accepts the theory of descent, 
ou Darwinism, § tyt in no degree the Darwinian causal explanation of 
this descent. “Was ich in diesen Berichten nachzuweisen suche, 
ist die Tatsache, dass der Darwinismus nunmehr bald der Ver- 
gangenheit, der Geschichte angehdrt, dass wir an seinem Sterbe- 
lager stehen und dass auch seine Freunde sich eben anschicken, 
ihm wenigstens noch ein anstandiges Begrabnis zu sichern” (p. 4). 
The valuable thing about the paper is that it is largely given to a 
gathering together of the anti-Darwinian opinions and declarations 
of numerous, mostly well-known and reputably placed biologists. 
Some of these declarations are interpreted by Dr. Dennert in a way 
that would probably hardly be wholly acceptable to the declarers, but 
for the most part the anti-Darwinian beliefs of these biologists are 
uumistakably revealed by their own words. Among the biologists 
and biological philosophers thus agglomerated into the camp of 


8 DARWINISM TO-DAY. 


anti-Darwinism are Wigand, Haacke, von Sachs, Goette, Kor- 
schinsky, Haberlandt, Steinmann, Eimer, M. Wagner, von Kolliker, 
Nageli, Kerner, F. von Wagner, Fleischmann, O. Schultze, O. Hert- 
wig, and others. This list includes reputable botanists, zoologists, 
and paleontologists. 

? For a recent account of such work, see Morgan, T. H., “Experi- 
mental Zodlogy,”’ 1907. 

3’ A. Fleischmann, professor of zoology in the University of Er- 
. langen, is the only biologist of recognised position, of whom I am 
An anti-evolu- aware, who publicly declares a disbelief in the theory 
tion university of descent. He seems to base his disbelief on the 
aiologist, fact that the phyletic (genealogic) series in numerous. 
animal groups are as yet unexplained. See his book, “Die De- 
scendenztheorie,” Leipzig, 1901. ‘‘Allein je mehr ich mich in die 
vermeintlichen Beweisgrtinde derselben [the theory of descent] 
vertiefte und durch Spezialuntersuchungen positive Anhaltspunkte 
fiir die Stammesverwandtschaft der Tiere zu gewinnen suchte, um 
so klarer stellte sich mir die Erkenntniss heraus, dass jene Theorie 
eben doch mehr nur ein bestrickender, Ergebnisse und Aufklarung 
vortauschender Roman sei, als eine auf positiven Grundlagen auf- 
gebaute Lehre.” (From the preface of this book). 

*A curious attempt to formulate a scientific theory explaining 
the conditions as we know them in the world of life, to replace the 

Friedmann’s theory of descent, is contained in a recent small book 
theory to replace called “Die Konvergenz der Organismen” (1904), 
evolution with by Hermann Friedmann. The author assumes that the 
divergence, diversity of organisms is the primary condition, and 
that their similarity has been brought about through convergence, as. 
opposed to the postulate of the theory of descent to the effect that 
diversity of life has grown out of primary identity or homogeneity. 
I quote (p. 12) as follows from Friedmann: “‘Diese Annahme, die in 
dem vorliegenden Buch vertreten wird, ist folgendermassen zu erlau- 
tern. Wir gehen von dem Hauptsatze aus, dass das Leben immer als. 
ein bestimmter, unwandelbarer Speziescharakter auftritt. Die spezi- 
fisch verschiedenen Lebensformen erscheinen jedoch einander 
angenahert, bezw. annaherbar, durch drei (Teil-) prinzipien, von 
denen das Leben beherrscht wird: Das Prinzip, vermoge dessen 
spezifisch verschiedene Formen  solche Ubereinstimmungen auf- 
weisen, die wir als primargesetzliche betrachten, nennen wir das. 
Prinzip der Homologie; als einen Ausfluss des Prinzips der Analo- 
gie bezeichnen wir diejenigen Ubereinstimmungen, die unter dem 
Einfltisse gleichwirkender Ausserer (mittelbar oder unmittelbar 
bewirkender oder selektiver): Bedingungen entstehen; und wir 
erkennen drittens die Macht und die Tragweite eines Prinzips der 


INTRODUCTORY: “DEATH-BED OF DARWINISM.” — 9: 


direkten Konvergenz, welches das Entstehen von Ubereinstim- 
mungen zwischen den Genossen einer Biosphare aus psychischen 
Ursachen bewirkt. Die drei Prinzipien bilden die Grundlage der 
Konvergenztheorie.” 

° Driesch, H., Biolog. Centralb., v. 16, p. 355, 1896. 

* Dennert, E., “Vom Sterbelager des Darwinismus,” p. 4, 1903. 

"Wolff, G., “Beitrage zur Kritik der Darwin’schen Lehre,” p. 54,, 
1808. 


CHAPTER II. 


DARWINISM AND EVOLUTION DEFINED AND 
DISTINGUISHED. 


Our manuals of zoology and botany contain the names 
and descriptions of about 400,000 living species of animals 
and 200,000 living species of plants. There are 
Possible = parts of the earth from which we have collected 
modes of origin ; ‘ 
of diverse plant aS yet only a few kinds of animals and plants, 
Ear ar merely the larger, more conspicuous or -more 
abundant kinds; there are no parts of the earth 
from which we are not constantly receiving reports of the 
discovery of “new” species—new, of course, simply in the 
sense that we have not known them before.” It is wholly 
certain that the number of different species, that is, kinds, 
of living organisms must number millions; various guesses,” 
all unimportant, have been made. Of the extinct species, 
those hosts of strange denizens of our changing earth in the 
ages gone, the number of recorded forms can at best be but 
the veriest fraction of the grand total of species that have 
actually existed. Now all these millions of kinds of animals 
and plants can have had an origin in some one of but three 
~ways; they have come into existence spontaneously, they | 
have been specially created by some supernatural power, or 
they have descended one from the other in many-branching 
series by gradual transformation.’ There is absolutely no 
scientific evidence for either of the first two ways; there is — 
much scientific evidence for the last way. There is left for 
the scientific man, then, solely the last; that is, the method 
Io 


DARWINISM AND EVOLUTION DEFINED. Il 


of descent.’ The theory of descent (with which phrase or- 
ganic evolution may be practically held as a synonym) is, 
then, simply the declaration that the various. 
living as well as the now extinct species of 
organisms are descended from one another and 
from common ancestors. It is the explanation of the origin 
of species accepted in the science of biology. (The natural 
question about the first species or the first several, if they 
appeared simultaneously, will receive attention later; the 
theory of descent explains the origin of kinds of life, not 
the origin of life.)° If such a summary disposal of the 
theories of spontaneous generation and divine creation is too 
repugnant to my readers to meet with their toleration, then, 
as Delage has pertinently said in connection with a similar 
statement in his great tome on “Heredity,” my book and such 
readers had better immediately part company; we do not 
speak the same language. | 

The theory of descent, long before it was fully set forth 
by Darwin in 1858 together with a definite and wholly 

Pre-Darwin. Plausible causo-mechanical explanation of it, 
ian recognitim had been foreshadowed and even fairly ex- ; 
ret at r plicitly formulated by various philosophical 
naturalists; among others, Goethe (1790) in Germany, 
Erasmus Darwin (1794) (grandfather of Charles Darwin) 
in England, Lamarck (1809) very definitely in France, 
Chambers in the “Vestiges of the Natural History of 
Creation” (1844), and Wallace (1858) coincidently with 
Darwin himself had all recognised descent as the only pos- 
sible scientific explanation of the origin of species and had 
offered explanations of the causal factors of this descent.’ 
Even in the far older writings * of the Greeks, most con- 
spicuously perhaps in the pages of Aristotle (350), may be 
found phrases and pages foreshadowing those of Lamarck, 
Wallace, and Darwin. ° But it was not until Darwin had 
backed up the formulation of the descent theory with that 


Theory of 
descent defined, 


12 DARWINISM TO-DAY. 


wonderful accumulation of illuminating and explaining 
facts, and with those always ingenious but ever candid and. 
supremely honest tryings-on of the theory to the various 
fact-bodies; that the Theory of Descent began 
Theory of to be spelled with capital letters in the biological 
sete creed.“ Nor was it merely good-fortune that: 
Darwin, led to the quick and‘ wide acceptance of the 
theory of descent when proposed by Darwin, 
while the same theory when proposed twenty years earlier by 
Lamarck found practically only rejection. ‘It was because 
to the old descent theory the new Darwinian theories were: 
added. It was because of that explaining Darwinism, which 
to-day is being so rigorously re-examined as to its validity, 
that the theory of descent took its definite place as the: 
dominant declaration in the biological credo. 

This Darwinism of 1858 and 1859 consisted of the selec- 
tion theories ; the Darwinian pangenesis of gemmules theory 
was a product of ten years later. It was the first of the 
Darwinian concessions to scientific anti-Darwinism. That 
is, it was a supporting hypothesis erected to strengthen a. 
foundation which was being weakened by the enemy’s 
attacks. Curiously enough this first Darwinian concession 
was made not on behalf of a true Darwinian principle, but 
for the sake of a Lamarckian principle which Darwin had 
thought necessary to include in his general conception of the 
transmission of variations. Even in the formulation of the 
true Darwinism, the selection theories, there must also be 
recognised the participation of other minds than that of 
Darwin. Malthus, who wrote, in 1826, of the over-supply 
and the consequent struggle in the human population and 
undoubtedly added much to Darwin’s confidence in his own 
conception of the prodigality of production and the necessary 
struggle for life throughout the world of organisms, and 
Wallace, who came to conclusions practically identical with 
Darwin’s at practically the same time, are men whose names 


DARWINISM AND EVOLUTION DEFINED. ry 


care ever to be associated with the theory of over-production, 
struggle, and selection. 
Darwinism may be defined, then, as a certain rational, 
‘causo-mechanical (hence, non-teleologic) explanation of the 
The Dar- origin of new species.” The Darwinian explana- 


winian expla- : : i 
nation ofde.  t10N rests on certain observed facts, and certain 


‘scent, inductions from these facts The observed . 


facts are: (1) the increase by multiplication in geometrical 
ratio of the individuals in every species, whatever the kind 
of reproduction which may be peculiar to each species, 
whether this be simple division, sporulation, budding, par- 
thenogenesis, conjugation and subsequent division, or 
amphimixis (sexual reproduction) ; (2) the always apparent 
slight (to greater) variation in form and function existing 
among all individuals even though of the same generation or 
brood; and (3) the transmission, with these inevitable 
slight variations, by the parent to its offspring of a form 
and physiology essentially like the parental. The inferred 
(also partly observed) facts are: (1) a lack of room and 
food for all these new individuals produced by geometrical 
multiplication and consequently a competition (active or 
passive) among those individuals having any cecologic rela- 


tions to one another, as, for example, among those occupying ° 


the same locality, or needing the same food, or needing each 
other as food; (2) the probable success in this competition 
of those individuals whose slight differences (variations) 
are of such a nature as to give them an advantage over their 
‘confreres, which results in saving their life, at least until 
they have produced offspring; and (3) the fact that these 
“saved” individuals will, by virtue of the already referred 
to action of heredity, hand down to the offspring their 
advantageous condition of structure and physiology (at 
least as the “mode” or most abundantly represented condi- 
tion, among the offspring). xy 
- The competition among individuals and kinds (species) 


% 


Rime wen» 


14 DARWINISM TO-DAY. 


of organisms may fairly be called a struggle. This is 


obvious when it is active, as in actual personal 
eee and battling for a piece of food or in attempts to 

capture prey or to escape capture, and less 
obvious when it is passive, as in the endurance of stress of 
weather, hunger, thirst, and untoward conditions of any 
kind. The struggle is, or may be, for each individual 
threefold in nature: (1) an active struggle or com- 
petition with other individuals of its own kind for 
space in the habitat, sufficient share of the food, and 
opportunity to produce offspring in the way peculiar and 
common to its species; (2) an active or passive struggle or 
competition with the individuals of other species which may 
need the same space and food as itself, or may need it or 
its eggs or young for food, and (3) an active (or more 
usually passive) struggle with the physico-chemical external 
conditions of the world it lives in, as varying temperature 
and humidity, storms and floods, and natural catastrophes 
of all sorts. For any individual or group of individuals any 
of these forms of struggle may be temporarily ameliorated, 
as is (1) the intra-specific struggle among the thousands of 
honey-bee individuals living together altruistically in one 
hive, or (2) the inter-specific struggle when two species 
live together symbiotically as the hermit crab* Eupagurus 
and the sea-anemone Podocoryne, or (3) the struggle 
against untoward natural conditions as in special times or 
places of highly favourable climate, etc. Or for any indi- 
vidual or group of individuals all forms of the struggle may 
be coincidently active and severe. ‘ The resultant of these 
existing conditions is, according to Darwin and his followers, 
an inevitable natural selection of individuals and of species. 
Thousands must die where one or ten may live to maturity 
(1. é., to the time of producing young). Which ten of the 
thousand shall live depends on the slight but sufficient ad- 
vantage possessed by ten individuals in the complex struggie. 


DARWINISM AND EVOLUTION DEFINED. 15, 


for existence due to the fortuitous possession of fortunate 
congenital differences (variations). The nine hundred and 
ninety with unfortunate congenital variations are extin- 
guished in the struggle and with them the opportunity 
for the perpetuation (by transmission to the offspring) of 
their particular variations. There are thus left ten to re- 
produce their advantageous variations. The offspring of 
the ten of course will vary in their turn, but will vary around 
the new and already proved advantageous parental condi- 
tion: among the thousand, say, offspring of the original 
saved ten the same limitations of space and food will again 
work to the killing off before maturity of nine hundred and 
ninety, leaving the ten best equipped to reproduce. ‘This 
repeated and intensive selection leads to a slow but steady 
and certain modification through the successive generations: 
of the form and functions of the species; a modification 
always towards adaptation, towards fitness, towards a 
moulding of the body and its behaviour to safe conformity 
with external conditions. The exquisite adaptation of the , 
parts and functions of the animal and plant as we see it 
every day to our infinite admiration and wonder has all 
come to exist through the purely mechanical, inevitable 
weeding out and selecting by Nature (by the environmental 
determining of what may and what may not live) through 
uncounted generations in unreckonable time. This is Dar- 
win’s causo-mechanical theory to explain the transformation 
_ of species and the infinite variety of adaptive modification. 
A rigorous automatic Natural Selection is the essential idea }4 “, 
in Darwinism, at least in Darwinism as it is held by the i 
present-day followers of Darwin. 

What auxiliary and supporting factors Darwin considered 
possibly or certainly of some influence or effect in species- 

Artificial © 4 fOrming we may postpone reference to until 
selection. our more particular examination of the natural 
selection theory in succeeding chapters of this book. Simi- 


16 DARWINISM TO-DAY. 


larly we may postpone any immediate reference to the facts 
of Artificial Selection (so important in any account of Dar- 
winism), that process, more or less familiar to us all, 
whereby the plant and animal breeders quickly and exten- 
sively modify the particular species with which they deal so 
as to produce, to order, as it were, manifold new kinds 
(races) of organisms. Despite the complexity of methods 
used in artificial selection, due to the combining of hybrid- 
isation, direct modification by varying nutrition, grafting, 
budding, etc., with selection, the basic and all-important 
essential is the selecting of a few individuals, namely, those 
which show the desired variations, to live long enough to 
produce offspring, and the killing out before maturity of the 
thousands of individuals that show unfortunate variations: 
(unfortunate, that is, from the breeder’s point of view). 
In the gardens of that extraordinary plant-breeder, Luther 
Burbank, in California, great bonfires of discarded seedlings 
correspond to the succumbing of the thousands in field and 
forest in the natural struggle for existence, while tenderly 
cared for little rows of pots contain the fortunate few which 
have withstood the rigours of the artificial competition. 
A part of Darwinism, which has already been named as 
such, is the theory of Sexual Selection; but the details of 
this, too, we may leave unexplained for the 
moment in order not too much to trouble the 
reader and the author, whose aim just now is 
to define the essential thought or conception in Darwinism, 
and to distinguish between this essential Darwinism and 
the different and wholly independent theory of descent. 
» Sexual selection is one of Darwin’s supporting theories 
which has nearly gone quite by the board. It is based on a 
postulated particular and limited kind of natural selection, 
not involving determination between life and death, but a 
determination between going childless and leaving posterity, 
—which is, after all, the essential determination in general 


Sexual se- 
lection, 


DARWINISM, AND EVOLUTION DEFINED. 17 


natural selection. But the assumed choice in the theory 
of sexual selection has a much less mechanical and auto- 
matically working basis, involves violent assumptions re- 
garding the zsthetic development of birds, butterflies, and 
spiders, and as we shall later see was one of the first of Dar- 
winian outworks to be sadly breached by attack. 
I hope now to have pointed out clearly in the preceding 
paragraphs the real’ distinction between the theory of 
descent and the theory of natural selection 
Theory ofde- (Darwinism). The bases, consisting of ob- 
scent and the ; 
theory ofnatural served facts and logical reasons, of the selec- 
 Soarvea tion theory, have been given; perhaps it were 
well to state briefly the bases, or sources of the 
scientific evidence for the theory of descent. This evi- 
dence is derived from three chief sources; the study of the 
comparative anatomy and structural homologies of organ- 
isms, the study of the prehistoric animals and plants, that 
is, paleontology or historical geology, and the study of 
ontogeny, or embryology, that is, the development of in- 
dividual animals and plants. The homologies or structural 
correspondence, in gross and in detail, which the study of 
animal and plant comparative anatomy reveals to exist in 
varying degrees among living and extinct kinds of organ- 
isms have but one possible scientific explanation : an explana- 
tion which serves at once to account for the existence of 
‘this correspondence and for its varying degrees. 
rani datt for This explanation is community of ancestry, the 
blood-relationship of organisms, the theory of 
descent. Similarly the facts revealed by the study of 
palzontology are explicable wholly satisfactorily by the 
theory of descent and in no single definitive instance do they 
contradict it. Finally, the facts and conditions relating to 
the embryology or ontogeny of animals and plants are 
similarly wholly in consonance with the theory of descent, 
although the brilliant positive evidence for the theory which 


18 DARWINISM TO-DAY. 


the first revealing of the phenomena of ontogeny led bi- 
ologists to expect and even to anticipate has confessedly not 
been forthcoming in that overwhelming measure hoped for. 
The evidence is excellent and positive and there is much of 
it, but the proof that man is descended from a fish because 
he has gill-slits at one period in his individual development 
is not of the sort to rely on too confidently. The recapitula- 
tion theory of Fritz Muller and Haeckel is chiefly con- 
Spicuous now as a skeleton on which to hang innumerable 
exceptions. But the scientific evidence for descent which 
embryology offers is neither weak nor Slight; it is only less 
overwhelming and all-sufficient than its too sanguine early 
friends and sponsors attributed to it. 

The specific character of the evidence for the theory of 
descent derived from the three chief sources just mentioned 
cannot claim our attention here. Knowledge of it is cer- 
tainly the attribute of all educated readers. If any one 
should desire to refresh his memory of it, he may readily do 
this by reading his Darwin, or Wallace, or Huxley, Haeckel, 
Spencer, Weismann, Romanes, Marshall, Cope,* e¢ al. 
What may for the moment detain us, however, is a reference 
to the curiously nearly completely subjective character of 
the evidence for both the theory of descent and natural 
selection. Biology has been until now a science of observa- 
tion ; it is beginning to be one of observation plus experiment. 
The evidence for its principal theories might be expected to 
be thoroughly objective in character; to be of the nature of 
positive, observed, and perhaps experimentally proved, facts. 
How is it actually? Speaking by and large we only tell 
ithe general truth when we declare that no indubitable cases 
of species-forming or transforming, that is, of descent, have 
been observed ; and that no recognised case of natural selec- 
tion really selecting has been observed. I hasten to repeat 
the names of the Ancon sheep, the Paraguay cattle, the 
Porto Santo rabbit, the Artemias of Schmankewitch, and 


DARWINISM AND EVOLUTION DEFINED. 19 


the de Vriesian evening primroses to show that I know my 
list of classic possible exceptions to this denial of observed 
species-forming, and to refer to Weldon’s broad-and 
narrow-fronted crabs as a case of what may be an observa- 
tion of selection at work. But such a list, even if it could 
be extended to a score, or to a hundred, of cases, is ludicrous: 
as objective proof of that descent and selection, under 
whose domination the forming of millions of species is sup- 
posed to have occurred. The evidence for descent is of 
satisfying but purely logical character; the descent hypoth- 


esis explains completely all the phenomena of homology, of 
paleontological succession, of ontogeny, and of geographi-. 


cal distribution; that is, it explains all the observed facts 


touching the appearance in time and place on this earth of 


organisms and the facts of their likenesses and unlikenesses: 
to each other, and this no other theory does. ‘The evidence 
for the selection theory we shall refer to in detail in the suc- 
ceeding chapters, so we may merely recall now that it also 
chiefly rests on the logical conclusion that under the 
observed fact of over-production, struggle is bound to 


occur; that under the observed fact of miscellaneous varia- - 


tion, those individuals most fortunate in their variations will 
win in the struggle; and, finally, that under the observed 
fact of heredity, the winners will transmit to their posterity 
their advantageous variations, all of which inter-acting facts 
and logically derived processes will be repeated over and 
over again, with the result of slow but constant modification 
of organic types, that is, formation of new species. In the 
light of this subjective character of the evidence for descent 
and selection, i#is with unusual interest that one notes the 
swift development of experimental and statistical investiga- 
tion in biology. Experiment and statistics are capable of 
mathematical treatment; biology may become an exact 
science instead of one solely of observation and induction. 

As with the conclusion of this chapter we are practically 


; 


20 DARWINISM TO-DAY. 


to conclude all reference to the theory of descent, which is 
to-day more than ever before an integral and unquestioned 
part of biological science, and to devote most of the rest of 
our discussion to the theory of natural selection, which 
is to-day being subjected to more searching scientific criticism 
than ever before since its proposal by Darwin, it will be well 
to distinguish, if we can, in the general influence that post- 
Darwinian biology has had on associated sciences and 
disciplines, that particular influence which each of these two 
great theories has had. So that if our faith in either is to 
be shaken we may recognise what effects on our sociologic, 
pedagogic, and philosophic beliefs this particular weakening 
of the biologic basis may have. 
' \ The relation of theology * to biology is concerned almost 
wholly with the theory of descent.“ The slow and gradual 
-forming of species including the particular one, 
Relation of “man, and their genetic relationship, the allying 
wees vagy: of man by blood with the lower animals—these 
philosophy, © .are the two biological conceptions (both in- 
cluded in the descent theory) which have been 
the chief points of attrition in the coming together of 
theology and biology. ' Darwinism specifically as such, that 
is, the selection principle, has had some special attention from 
theologians because of its substitution of a causo-mechanical 
for a teleological explanation of species-forming, and because 
it differs in its interpretation of the time necessary for peopling 
the globe with a variety of organic forms from the inter- 
pretation, or rather explicitly specific statement, of the first 
chapter of Genesis. But on the whole the Darwinian selec- 
tion theories could be utterly done away with without making 
any appreciable change in the existing relation between 
theology and biology. Huxley said this to the theologian 
Darwinophobes many years ago. 
And practically so with philosophy.’ It is the trans- 
formation principle, the principle of continuity, of monism 


DARWINISM AND EVOLUTION DEFINED. 21 


in Nature that Evolution represents, that philosophy is con- 
cerned to consider. Not the actual how of the modification 
and transformism of animal and plant life. 
In pedagogy it is also the theory of descent rather 
than the selection theory which has been drawn on for 
some rather remarkable developments in child- 
Relation of = study and instruction. Unfortunately it is ex- 
theory of descent ‘ 
topedagogy, actly on that weakest of the three foundation 
pillars of descent, namely, the science of em- 
bryology with its Millerian-Haeckelian recapitulation theory 
or biogenetic law, that the child-study pedagogues have 
builded. The species recapitulates in the ontogeny (develop- 
ment) of each of its individuals the course or history of its 
phylogeny (descent or evolution). Hence the child corre- 
sponds in different periods of its development to the phyletic 
stages in the descent of man. As the child is fortunately 
well by its fish, dog, and monkey stages before it comes into 
the care of the pedagogue, he has to concern himself only 
with its safe progress through the various stages of pre- 
historic and barbarous man. Detect the precise phyletic 
stage, cave-man, stone-age man, hunter and roamer, pastoral 
man, agriculturalist, and treat with the little barbarian ac- 
cordingly! What simplicity! Only one trouble here for 
the pedagogue; the recapitulation theory is mostly wrong; 
and what is right in it is mostly so covered up by the 
wrong part, that few biologists longer have any confidence 
in discovering the right. What then of our generalising 
friends, the pedagogues? 
Finally in sociology,’ more particularly biological soci- 
ology. Here again, to my eyes, much biological sociology 
rests on two very insecure bases: (1) a too 
age ueae slight acquaintance with biology on the part 
to sociology, of the biological sociologist, and, (2) an 
acceptance of, and confidence in, certain biologi- 
cal theories which are certainly unwarranted, and are not 


22 DARWINISM TO-DAY. 


at all shared by the biologists themselves. Biological science 
contains much that is proved and certain; but also much 
that is nothing more than working hypothesis, provisional 
theory, and anticipatory generalisation. As the proved part 
is largely of the nature of facts of observation, isolated and 
unrelated, and the unproved part is composed of the large 
and sweeping generalisations, the plausible, provisional ex- 
planations, such as the various theories of heredity, of the 
results of struggle, of the development of mutual aid, etc., 
that is, is exactly the sort of material that the sociologist 
needs to weave into his biological foundations for the 
sociologic study of man, it is exactly this unproved part of 
biology that the searching sociologist carries home with him 
from his excursions into the biological field. The recapitula- 
tion theory looms up large and familiar in biological soci- 
ology; it is mostly discredited in biology. The inheritance 
of acquired characters serves as basis for much sociology ; 
most biologists believe it impossible. The selection theories 
are gospel to some sociologists ; they are the principal moot 
points in present-day biology. And soon. Biology is not 
yet come to that stage in its development where it can offer 
many solidly founded generalisations on which other sciences 
can build. The theory of descent is one such safe great 
generalisation; but perhaps Darwinism is not another. At 
least many scholars do not believe that it is. 


APPENDIX. 
pf . ets alone entomologists have estimated, on a basis 
Or ta PF eh so species being annually found and described, 
and on th “sos -¢ degree to which the entomological explora- 


tion of the earth has been carried, that over two million species 
must be in present existence. 

* See H. F. Osborn’s “From the Greeks to Darwin” (1895) for a 

2 careful history of the unfolding of the descent idea; 

istory of de- Ver 

scent theory, see also Edgar Dacqué, “Der Descendenzgedanke und 

seine Geschichte,” 1903; also Carus, J. V., ‘“Geschichte 

der Zoologie bis auf J. Miller und C. Darwin,” 1872; also Clodd, 


DARWINISM AND EVOLUTION DEFINED. 23 


Edw., “Pioneers of Evolution from Thales to Huxley,” 1897; 
and Quatrefages, A. de, ‘““Les Emules de Darwin,” 2 vols., 1894. 

®* Many of the hermit crabs (Paguride) which live in the dis- 
carded shells of gasteropod molluscs have some species of small 
colonial polyp, as Podocoryne, attached to and partly covering the 
shell. The polyp colony profits by being carried about and by obtain- 
ing bits of food when the crab has succeeded in catching prey and 
is tearing it to pieces with his claws, while the crab profits by the 
protection afforded it by the stinging threads and nettle cells of 
the polyp. Esig saw in the aquaria of the zoological station at 
Naples a small octopus which was trying to insert one of its ten- 
tacles into a shell to get the crab, quickly driven away by the many 
stinging threads with which it was caressed by the polyp colony 
seated on the outer surface of the shell. This symbiotic life between 
hermit crab and polyp goes so far with some species that the hermit 
crabs never rest until they have a polyp colony seated on their shell. 

* Among more recent books stating the essential points in this 
evidence may be mentioned Conn’s “Evolution of To-day,” 1889; 

Books giving Wallace’s ‘‘Darwinism,” 1891; A. M. Marshall’s 
the evidences for ‘““Lectures on the Darwinian Theory,” 1894; Ro- 
descent. manes’s “Darwin and After Darwin,’ Vol. I, 1896; 
Klaatsch’s ‘‘Grundziige der Lehre Darwins,”'1900; Metcalf’s “Out- 
line of the Theory of Organic Evolution,” 1904; Weismann’s 
“Vortrage tiber Descendenztheorie,”’ 2 vols., 1902; Eng. trans. 2 
vols., 1904; Lotsy, J. P., “Vorlesungen iiber Descendenztheorien, 
mit besonderer Beriicksichtigung der botanischen Seite der Frage,” 
2 vols., Vol. I, 1906; Jordan and Kellogg, “Evolution and Animal 
Life.” 1907. 

* For an interesting discussion from the modern point of view of 
the relation between Darwinian biology and theology see Haeckel, 


Discnssionsof Ernst, “Der Monismus als Band zwischen Religion 
relation ofde- und Wissenschaft,’ 1893; also Vetter, Benjamin, 
scentandthe- “Die moderne Weltanschauung und der Mensch,” 
Beey: 1903; also Wasmann, Erich, “Die moderne Biologie — 


9 


und die Entwicklungstheorie,” 1904. (Author is a Jesuit priest whose 
remarkable studies on ants and their messmates have made him well 
known to biologists. He accepts the theory of descent, with the ex- 
clusion of man from the evolution series.) See also Hutton, F. W., 
“The Lesson of Evolution,” 1902. In this book the author takes a 
strong stand for dualism, making the point that the theory of evo- 
lution has rescued philosophy from a rigidly monistic materialistic 
basis (a mind-in-all-matter theory), and has made necessary a dual- 
istic theory (mind-and-matter theory) because of the necessity of 
postulating the beginning of life and a beginning of mind. The 


24 DARWINISM TO-DAY. 


theory of evolution rescues religion from Pantheism, and puts it on a 
Theistic basis. “It is true, as Pantheists urge, that their only experi- 
ence of mind is in connection with matter, but so far as we know 
mind is connected only with one kind of matter called protoplasm, 
which cannot possibly exist throughout the universe. Consequently 
mind must either be absent in large portions of matter or it must 
be associated with that matter in some way which quite transcends 
their experience. So that we have no more experience of mind 
universally distributed through matter than we have of mind dis- 
tinct from matter. And the argument for Pantheism breaks down.” 
See also Le Conte, Jos., “Evolution, its Nature, its Evidences and 
its Relation to Religious Thought,” 1891. 
*Of course many books and papers concerning the relation of 
biology to philosophy have been written. A good introduction to 
Discussions of the subject is Eugen Dreher’s “Der Darwinismus und 
relation of biol- seine Stellung in der Philosophie,” 1877; see also Ver- 
ogy and philoso- worn, Max, ‘““Naturwissenschaft und Weltanschauung,” 
phy: 1904; also Adickes, Erich, “Kant contra Haeckel,” 
1901; also Emil du Bois-Reymond’s ‘“‘Uber die Grenzen des Naturer- 
kennens,” and “Die Sieben Weltrathsel”’; also Haeckel’s “Die Welt- 
rathsel” (trans. in English as ‘‘The Riddle of the Universe”); see 
also Schurman, J. G., “The Ethical Import of Darwinism,” 1888; 
also Huxley, “Evolution and Ethics and Other Essays,” 1894; see 
also Reinke, J., “‘Einleitung in die Theoretische Biologie,” 1901. 
The author sets out in this book the philosophic notions of Hart- 
mann, Lotze, Wundt, Muller and others concerning the principles 
and laws of biology, and does this definitely enough to make his 
book a pretty good compend of philosophico-biology. 
"See* Herbert Spencer’s ‘“‘Principles of Sociology”; also Lester 
Ward’s “Biological Sociology”; also Benjamin Kidd’s “Social Evo- 
lution”; also Curt Michaelis, ““Prinzipien der nattir- 
Biology and : : 5 : 
sociology. lichen und sozialen Entwicklungsgeschichte des Men- 
schen,” 1904; also ‘“‘Darwinismus und Sozialwissen- 
schaft,” 1903; see also Schallmeyer, W., “Vererbung und Auslese 
in Lebenslauf der Volker,” 1903. 


* The books and papers referred to in notes 5, 6, and 7 are simply 
certain ones that have particularly interested the author. The lists 
of references make not the slightest pretence to guide the general 
reader interested in these special subjects. 


GEEAB DERE DLE 
DARWINISM ATTACKED. 


ATTACKS on Darwinism have been made, of course, ever 
since there was any Darwinism to attack. In those first days 
(and months and years) after the “Origin of 
Species” was published there were the liveliest 
of times for Darwin and his supporters; or 
rather chiefly for the supporters. Darwin wisely kept 
aloof from the debates. But for the first band of followers’ 
with the indefatigable, the brilliant, and wholly competent 
Huxley at its head, there was no lack of opportunities for 
jousting. The issue was never doubtful; Huxley and his 
informed and equipped scientific companions against the 
scientifically ignorant, angry, incautious, and dogmatic 
Bishop Wilberforces had unfair odds. The victory came 
swiftly and brilliantly to the Darwinians. At this time there 
was little distinction made between Darwinism and Evolu- 
tion. It was really a battle by the theologians against the . 
theory of descent. And the theory of descent was, and is, 
invulnerable. 

Since those warring days of the ’6o’s ‘the theory of 
descent has been assailed no more, that is in any important, < 

or even interesting way. And'the true Darwin- \ 
Evie ca dks ism, the selection doctrine, has also been sub- | 
of Darwinism. ject to no conspicuous and popularly recognised 
attack. The educated public accepted the re- 
sults of the first battle as final, and it quietly began to 
rearrange its thought and to some degree its actual ways 
25 


"Early attacks 
_ on Darwinism. 


26 DARWINISM TO-DAY. 


of living in accordance with these newly discovered condi- 
tions of life. Nevertheless there has been from the day 
of the close of the great first battle to the present moment a 
steady and cumulating stream of scientific criticism * of the 
Darwinian selection theories.~ In the last few years, it has, 
as already mentioned in the preface and introductory chapter 
of this book, reached such proportions, such strength and 
extent, as to begin to make itself apparent outside of strictly 
biological and naturo-philosophical circles. Such older 
biologists and natural philosophers as von Baer, von Kolli- 
ker, Virchow, Nageli, Wigand, and Hartmann, and such 
others writing in the nineties and in the present century as 
von Sachs, Eimer, Delage, Haacke, Kassowitz, Cope, 
Haberlandt, Henslow, Goette, Wolff, Driesch, Packard, 
Morgan, Jaeckel, Steinmann, Korschinsky, and de Vries, 
are examples which show the distinctly ponderable char- 
acter of the anti-Darwinian ranks. Perhaps these names 
mean little to the general reader; let me translate them into 
the professors of zoology, of botany, of paleontology, and 
of pathology, in the universities of Berlin, Paris, Vienna, 
Strassburg, Tubingen, Amsterdam, Columbia University, 
etc. Now without knowing the man personally, or even 
through his particular work, the general reader can safely 
attribute to men of such position a certain amount of 
scientific training, of proved capacity, and of special ac- 
quaintanceship with the subject of their discussion. One 
does not.come to be a professor of biology in Berlin or 
Paris or Columbia solely by caprice of ministers of educa- 
tion or boards of trustees; one has proved one’s competency 
for the place. To working biologists the names—I have 
given, of course, only a selection, and one particularly made 
to show variety of interest (botany, zoology, palzontology, 
pathology )—mean even more than the positions. “They are 
mostly associated with recognised scientific attainment and 
general intellectual capacity. 


DARWINISM ATTACKED. 27 


Among the critics of the selection theories we must note 


two groups, differing in the character of their criticism \,.~ 


Two croup? of Ole in degree than in kind, perhaps, but still _ 
scientificat- importantly differing. One group denies in — 
eee toto any effectiveness or capacity for species- 
forming on the part of natural selection, while the other 
group, a larger one, sees in natural selection an effective 
factor in directing or controlling the general course of 
descent, holding it to adaptive lines, but denies it outright 
any such Allmacht of species control as the more eager 
selectionists, the so-called’ neo-Darwinians or Weismann- 
ians, credit it with. This larger group of critics sees in 
natural selection an evolutionary factor capable of initiating 
nothing, dependent wholly for any effectiveness on some 
primary factor or factors controlling the origin and direc- 
tion of variation, but wholly capable of extinguishing all 
unadapted, unfit lines of development, and, in this way, of 
exercising decisive final control over the general course of 
descent, i. e., organic evolution. Another classification of 
critics may be made on the basis of pure destructiveness on 
the one hand as opposed to destructiveness combined with 
constructiveness on the other. That is, some critics of selec- 
tion, as Wolff, Pfeffer, Driesch, e¢ al., are content with doing 
their best to reveal the incapacity of Darwinism; others, 
on the contrary, come with certain more or less well-outlined 
substitutionary theories in their hands. Eimer with his 
theory of orthogenesis, and Korschinsky and de Vries with 
their theory of mutations, are examples of the latter class. 

The general impression left on one after a considerable 

course of anti-Darwinian reading ranging all the way from 

the extreme attitude and the violence of Den- 

ede Pie nert, “Fleischmann, Wolff, and. Coe, >to the 

ness in substitu- tempered and reserved criticism of Delage and 
tion. : ° : . 

de Vries, is that there is a very real and effective 

amount of destructive criticism for Darwinians to meet; and 


28 DARWINISM TO-DAY. 


at the same time a curious paucity of satisfactory or at all 
convincing substitutionary theory offered by the anti- 
Darwinians to replace that which they are attempting to 
dethrone. The situation illustrates admirably the varying 
worth of a few facts. A few stubborn facts of the wrong 
complexion are fatal things for a theory; they are immensely 
effective offensive weapons. But these same few facts make 
a pitiable showing when they are called on to support a 
theory of their own. It was exactly the greatest part of| 
Darwin’s greatness, it seems to me, that he launched his 
theory only after making the most remarkable collection of | 
facts yet gathered together in biological science by any one 
man. Testing his theory by applying to it successively | 
fact after fact, group after group and category after category 
of facts, he convinced himself of the theory’s consonance 
with all this vast array of observed biological actuality. 
Compare the grounding of any of the now offered replacing 
theories with the preparation and founding of Darwinism. 
In 1864 von Kolliker,” a great biologist, convinced of the 
incapacity of natural selection to do the work assigned it by 
its founders and friends, suggested a theory of the origin of 
species by considerable leaps; in 1899, Korschinsky,* on the 
basis of some few personal observations and the compiling 
of some others, definitely formulated a theory of species- 
forming by sudden considerable variations, namely, muta- 
tions; in 1901 and 1903 appeared the two volumes of de 
Vries’s “Die Mutationstheorie,’ in which are revealed the 
results of long years of careful personal observation, in 
truly Darwinian manner, directed toward the testing and 
better grounding of this mutationstheorie of species-origin.. 
The results are: out of many plant species studied, a few 
show at certain times in the course of numerous generations 
a behaviour in accordance with the demands of a theory 
of species-forming by sudden definitive modification; that 
is, species-forming by mutations. The mutations-theory 


DARWINISM ATTACKED. 29 


thus launched is offered as a substitute for the natural 
selection theory obviously weakening under the fire of 
modern scientific criticism. But however effective de 
Vries’s facts are in proving the possibility of the occurrence 
of other variations than those fortuitous ones occurring in 
continuous series from mean to opposite extremes which Dar- 
win recognised as the basis of species-forming, and however 
effective they are in proving the actual production of three 
or six or ten species by mutation, and however effective in 
both these capacities they are as weapons of attack on the 
dominance of the Darwinian theory of species-making, 
how really inadequate are they to serve as the basis of a 
great all-answering theory explaining, in a causo-mechanical 
way, the facts of descent, or even the primary facts of gen- 
eral species-forming. And yet the first American book * 
(from the pen of one of America’s foremost biologists) to 
_ discuss the modern phase of unrest and dissatisfaction in 
evolutionary matters, practically accepts the mutations- 
theory as a substitute for the selection theory of species- 
forming. It cannot be, it seems to me, that Professor 
Morgan is so satisfied with the mutations-theory, that he 
clutches it up, hardly definitely formed and cooled, from the 
de Vriesian moulds, but that he is, like many another present- 
day biologist, so profoundly dissatisfied with the natural 
selection theory. For my part it seems better to go back 
to the old and safe Jgnoramus’ standpoint. 

But I have been led to anticipate my conclusions; let us 
make another beginning with the real undertaking of this 
chapter and get to the actual specifications of ‘Darwinism 
Attacked.’ We shall concentrate the attacks and attackers in 
this and the two following chapters ; then include in the suc- 
ceeding two the defence and the defenders, and in the next 
four chapters the various supporting and substitutionary 
theories offered by the friends and foes of Darwinism. 
Finally, in the last chapter we shall set out what we can 


30 DARWINISM TO-DAY. 


discover, in the haze of the smoke of battle, of the actual 
present state of the besieged and besiegers. 

Distinctly the most comprehensive, the fairest-minded 
review of gegen-und-fiir Darwinismus in recent literature is 
Plate’s extension of his address, “Uber die Bedeutung des 
Darwin’schen Selectionsprincips,’ made in Hamburg be- 
fore the Deutsche Zoologische Gesellschaft in 1899. To 
this review, as published in 1903 after being extended and 
brought up to date, I beg to acknowledge a special indebted- 
ness in my present attempt to get together the more im- 
portant criticism, both adverse and defensive, of Darwin. 
I have, however, assiduously sought out (with the help of 
librarians and my indefatigable Leipzig book-dealer friend 
Bernh. Liebisch), and perused the original pourings-forth of 
criticism and vilification even to the reading of some matter 
written by certain Roman Catholic priests with a consider- 
able amateur interest in natural history and a strong pro- 
fessional interest in anti-Darwinism! But Plate has been 
a guiding hand in this search for active attacks and de- 
fence. 

The natural selection theory as an all-sufficient explanation 
of adaptation and species-forming has always had a weak- 

ness at its base; it depends absolutely, of course, 
ogee on the pre-existence of variations, but it itself 
on variation. | has no influence whatever on the origin or con- 
. trol of these variations except in so far as it may 
‘determine what individuals shall be permitted to give birth 
to other individuals. Now one of the chief problems in 
biology is exactly that of the origin, the causes, and the 
primary control of these congenital variations.*° Three 
principal explanations, no one of them experimentally 
proved or even fairly tested as yet, have been given of this 
actually occurring congenital variation, viz., (1) that there 
exists in the germ-plasm an inherent tendency or capacity 
to vary so that there is inevitable variation in all individuals 


DARWINISM ATTACKED. eG 


produced from germ-plasm, this variation being wholly 
fortuitous and fluctuating according to some (the belief of 
Darwin and his followers), or, according to others, this 
variation following certain fixed or determinate lines (de- 
terminate variation, orthogenetic variation, etc.) ; (2) that 
amphimixis, i. e., bi-parental parentage, is the principal 
cause of variation, it seeming logical to presume that indi- 
viduals produced from germ-cells derived from the fusion 
of germ-plasm coming from two individuals more or less 
unlike would differ slightly from either of the parental 
individuals; and (3) that congenital variation is due to the 
influence of the ever-varying environment of the germ-cell 
producing individuals. The objections to any one of these 
theories may be very pertinent, as when one says regarding 
the first that calling a thing ‘ 
any degree a phenomenon for which we are demanding a 
causo-mechanical explanation; or of the second that it has 
been proved * that individuals produced parthenogenetically, 
that is, from an unmated mother, vary and in some cases 
vary even more than do other individuals of the same species 
produced by amphimixis; or of the third that as far as our 
study of the actual processes and mechanism of the produc- 
tion of germ-cells and of embryos has gone, we have found 
no apparent means whereby this influence of the ambient 
medium can be successfully impressed on the germ-plasm. 
But however pertinent the objections to the why of varia- 
tion may be they do not in any way invalidate the fact that 
variations do continuously and inevitably occur in all indi- 
viduals, and that while many of these variations are recog- 
nisably such as have been impressed on the individual during 
its personal development as immediate results of varying 
temperature, amount or kind of food, degree of humidity, 
etc., to which it may be exposed in its young life, others 
seem wholly inexplicable on a basis of varying individual 
environment and are certainly due to some antenatal influ- 


‘inherent” is not clearing up in - 


32 DARWINISM TO-DAY. 


ence acting on the germ-plasm from which the embryo is 
derived. 
Now the natural selection theory, in its Darwinian and 
neo-Darwinian form, presupposes fortuitously occurring 
congenital variations of practically infinite 
Darwinian, or variety in all parts of all organisms. Actual 
continuous, varla- ; 
tion according to Observation shows that all parts of all organ- 
Seales : isms do vary and that they vary congenitally, 
that is, independently of any immediate in- 
fluence during development exercised from without by 
environmental conditions, as well as in response to these 
environmental influences, and finally that in many cases this 
variation is fortuitous, that is, that it occurs according to 
the laws* of chance. The industrious statistical study of 
variations, including the tabulation of the variation con- 
dition in long series of individuals of the same species or 
race and the mathematical formulation of this variation 
condition, have shown that in many specific cases, studied 
in numerous kinds of animal and plant forms, the character 
of the variation in any particular character may be truly 
represented (with close approximation) by the mathematical 
expression and curve which would exactly define the condi- 
tion in which the variation would exist if it actually followed 
the law of error. It is these continuous series of slight 
variations, these variously called fluctuating, individual, or 
Darwinian variations, occurring in all organisms at all times 
and often following, in their occurrence, the laws of chance, 
on which Darwin’s theory of species-forming by natural 
selection is based. But this same industrious statistical 
and quantitative study of variation, which has proved 
that some variations do occur regularly, fluctuating 
around a mean or mode, has shown, as well, that in 
many cases the variations distinctly tend to heap up 
on one side or the other of the mean, that is, that they 
tend to occur along certain lines or toward certain direc- 


DARWINISM ATTACKED. ao 


tions rather than uniformly out in all directions. Also it 
is true, and this has of course been long known, that by 
no means all variations are so slight nor in 
such perfectly gradatory or continuous series 
as is true of the gradatory Darwinian variations. 
“Sports” have been known to breeders of plants and animals 
ever since plant and animal breeding began. Bateson has 
filled a large book * with records of “discontinuous varia- 
tions” in animals ;’variations, that is, of large size and not 
occurring as members of continuous gradatory series.’ So 
that biologists are acquainted with many cases of variation 
that seem to be of a kind, on to exhibit a tendency, to in- 
stitute special directions of development, and thus not to be 
of the simple, non-initiating, inert character of the fortuitous, 
slight, fluctuating variations, among which natural selection 
is presumed to choose those that are to become the be- 
ginnings of new lines of modification and descent. Many 
biologists believe firmly that variations occur in many 
special cases, if not in most cases, only along certain special 
lines. Palzontologists believe, practically as a united body, 
that variation has followed fixed lines through the ages; 


Discontinuous 
variation, 


“ 


on 


on 


that there has been no such unrestricted and utterly free play | 
of variational vagary as the Darwinian natural selection . 


theory presupposes. 
Now it is at least obvious that natural selection is abso- 
lutely limited in its work to the material furnished by varia- 
tion; so that if variation occurs in any cases 
Determinate Only along certain determinate lines selection 
variation as@ = =¢an do no more than make use of these lines. 
species-forming i Tees ; 
factor. Indeed if variation can occur persistently along 
determinate lines natural selection’s function in 
controlling evolution in such cases is limited to the police 
power of restricting or inhibiting further development along 
any one or more of these lines which are of a disadvan- 
tageous character, that is, a character which handicaps or 


Naw 


34 DARWINISM TO-DAY, 


destroys the efficiency of its members in the struggle for life. 
The question in many men’s mouths to-day is, Why may not 
variation be the actual determinant factor in species-forming, 
in descent? It actually is, respond many biologists and 
palzontologists. | 

Even Darwin believed such determinate variation to occur, 
as is indicated by repeated statements in the “Origin of 
Species.” In chapter iv he says (to refer to but a single 
one of these admissions) : “It should not, however, be over- 
looked that certain rather strongly marked variations, which 
no one would rank as mere individual differences, fre- 
quently recur owing to a similar organisation being similarly 
acted on—of which fact numerous instances could be given 
with our domestic productions. In such cases, if the vary- 
ing individual did not actually transmit to its offspring its 
newly acquired character, it would undoubtedly transmit to 
them, as long as the existing conditions remain the same, 
a still stronger tendency to vary in the same manner. There 
can also be little doubt that the “tendency to vary in the 
same manner has often been so strong that all the individuals 
of the same species have been similarly modified without the 
aid of any form of selection’ Or only a third, fifth, or 
tenth part of the individuals may have been thus affected, of 
which fact several instances could be given. Thus Graba 
estimates that about one-fifth of the guillemots in the Faroe 
Islands consist of a variety so well marked, that it was 
formerly ranked as a distinct species under the name of 
Uria lacrymans. In cases of this kind, if the variation were 
of a beneficial nature, the original form would soon be sup- 
planted by the modified form, through the survival of the 
fittest.” 

This problem of the existence or non-existence of deter- 
minate variation is taken up in such detail in connection with 
the explanation and discussion of various auxiliary or alter- 
native theories of species-forming in later chapters of this 


DARWINISM ATTACKED. 35 


book that it need not detain us now. But to my mind it is 
one of the most important matters in connection with the 

ty eee whole great problem of descent, that is, of 
nate variation €volution. It is the basic problem of evolu- 
exist 7 tion, for it is the problem of beginnings. 
Selection, isolation, and the like factors are conditions 
of species-forming; variation is a prerequisite, a sine 
qua non. True variation must have its causes, and these 
causes are to be determined before an actual causo-me- 
chanical explanation of evolution can ever be found. But 
the determination of the relation of variation to species- 
forming is certainly the first step now necessary in our 
search for the basic factors, the real first causes of species 
change. 

But even in those cases where there may exist unrestricted 
indeterminate fluctuating variation in continuous series ac- 

What does  COrding to the law of error, what is it that this 
fluctuating vati- variation really offers natural selection to 
ation offer selec- : 
tion as a basisfor WOTK on? Remember what natural selection 
species-forming? is : the saving of one or ten by the actual killing 
of the thousand or ten thousand because in the struggle for 
existence the variations of the one or ten are of sufficient 
advantage to have a life-or-death-determining value. Now 


between any two successive individuals in a series arranged | 


on a basis of the variations in any one character of any one 


organ or function, the difference is extremely slight, too | 


slight, one is certain, to be, in most cases, of life or death 


value. But even if one’s conception of the absolute inten-. 


sity of the rigour of the personal struggle leads to a 
logical conception of an absolute advantage in any differ- 
ence, however slight, in a favourable direction, it is wholly 
possible that for any other characteristic equally important 
in the struggle the two individuals may be in exactly reversed 
position, the one possessing the infinitesimal advantage in 
strength say, possessing an infinitesimal disadvantage in 


36 DARWINISM TO-DAY. 


sharpness of claw or in agility. What of the chances for 
such a necessary coincidence in the one individual of favour- 
able variations in all the ways necessary to create a real life- 
or-death-determining advantage? The law of probabilities 
answers that much to the dismay of the Darwinian. But, 
again, why not compare the chances in the struggle of two 
individuals not standing side by side in a variational series, 
but at two extremes of the range; the difference here can be 
considerable, can be of positive advantage or disadvantage. 
Yes, but again comes the’ necessity of presupposing a coin- 
cidence of other advantages or at least of no coincidence of 
balancing advantages and disadvantages. But even more 
fatal is the condition that. if an extreme variation in some one 
character could be of a life-preserving advantage, yet by the 
law of probabilities (and by the tale of actual observation) 
those individuals standing at the extremes of the range of 
variation are very, very few compared with those standing 
nearer the mean, or mode, of the series, and there would 
be almost a certainty of such an extreme-charactered sur- 
vivor not finding a similar form with which to mate and thus 
insure perpetuation of the advantage, the mating of the 
individuals admittedly not depending on any necessary 
similarity in variation (unless the varying characteristics 
happen to be actually concerned with the mating act: see 
later discussion of biological isolation, chapter ix). Con- 
siderable variations, the only ones of apparent worth in a 
life-and-death struggle, are in such meagre disproportion 
to the less considerable that they are inevitably swamped, 
extinguished, in miscellaneous cross-mating. 

Let us consider a little more in detail each of the various 
objections mentioned in the last few pages. Only the student 

Tlentiers of systematic (classificatory ) zoology or botany 
of fluctuating can realise how slight and insignificant are the 
Bence various miscellaneous individual variations 
which make up that basis of ever-present, myriad-faced, 


DARWINISM ATTACKED. 37 


fortuitous, fluctuating variability on which the whole great 


structure of the selection theory is based. Yet any one’s 


common sense and his intuitive comprehension of what 
life-and-death value is in an animal’s battle with another, 
with foreign enemies, or with inclement Nature, make 
this objection of “no handle for natural selection in mis- 
cellaneous slight variation” thoroughly appreciable. Polar 
bears are probably descended from brown; and their white 


fur coat is probably an advantageous adaptation in their 
life in the Arctic. But did the fortuitous appearance in his 


coat of a spot of white hairs as large as a dollar or a pancake 


give some ancient brown bear such an advantage in the “< 


struggle for existence as to make him or her the fore- 
runner of a new and better-adapted sort of bear? The 


giraffe’s long neck is very much worth while to it; it gets 


leaves from the higher branches unattainable by the short- 
necked animals who find food in the same range. But dida 
millimetre or even an inch of extra neck appearing as 
individual variation in an ancestral short-necked giraffe 
kind give natural selection a handle with which to grind out 
a new species? The consideration of the usefulness of 
slight variations too often leads to an argument for their 
usefulness on the same grounds as sustain the belief that 
the hound will never catch the hare which goes one-half as 
fast as the dog. For each time the hound covers the given 


stretch that lies between him and the hare at any given, 


moment the hare will be just one-half that distance in 
advance—and though the distance will get ever shorter and 
shorter the hare will ever be one-half the last distance ahead. 
So say the sophists. As a matter of fact the hound gets the 
hare. 

Spencer’s example of the femur of the whale is a striking 
illustration of the reality of the absurdity connected with 
the argument of change on a basis of the selection of in- 
finitesimal differences. The femur of the whale, says 


aR Ane OR FE) 


38 DARWINISM TO-DAY. 


Spencer, is evidently the atrophied rudiment of a bone once 
much larger. It weighs now about one ounce, less than a 
millionth of the weight of the whole body. 
Spencer’s ex- : : 

ample ofthe Let us suppose that when it weighed two 
alae Ran ounces an individual had a femur which by 
variational chance weighed but one ounce. 
What advantage over other whales would the difference give 
it? What fraction of the daily nourishment would this ad- 
vantageous variation permit the fortunate whale to add to its 
stored fat. instead of spending it on an extra ounce of useless 
femur? Who would dare claim that this variation would 
aid in success in the struggle for existence? And yet this is 
the argument for the reduction of useless organs through 
the influence of natural selection. Roux and Weismann, 
realising the absurdity of the argument, have put forward 
two theories, one called the “battle of the parts” and the 
_ other the “theory of germinal selection” to aid the selection 
theory to explain the degeneration and reduction of organs. 
The reader will find these theories explained in chapter viii. 
Every student of systematic zoology or botany has a keen 
realisation, too, of the fact that a majority of the distinguish- 
ing characters which he recognises in the vari- 
Many species ous species and genera that. come under his 

‘characters of no . 
atility. eye are of a sort that reveal to him no trace of 
particular utility or advantage. Indeed he can 
go farther and express, to himself at least, his conviction 
that many of these slight but constant specific differences *° 
can actually. have no special advantageousness about them. 
One’s experience as an observer of nature and one’s common 
sense combine to protest against that easy and sweeping 
answer of the Darwinians: “shall ‘poor blind man’ say what 
characteristic, however. slight and insignificant, is or is not 
of advantage in the great complex of nature?” As the 
whole question after all resolves itself into one for which 
“poor blind man” is attempting to find an answer satisfying 


DARWINISM ATTACKED. 39 


to his own understanding, however short of perfection and 
omniscience that is, he is bound to answer the subsidiary 
problems such as usefulness or non-usefulness on a basis of 
his own seeing and understanding capacity. As a matter 
of fact the indifference of many specific characteristics of 
organisms is not denied by selectionists. Romanes** was 
perhaps the first representative Darwinian, after Darwin 
himself, to admit this. But many biologists say, further, on 
a basis of their experience as observers, that these very 
indifferent, meaningless (as far as utility goes) mor- 
phological characteristics and differences are much more 
constant in their character than*the obviously adaptive, 7. e., 
useful ones. However, as pointed out first by Nageli, accord- 
ing to the selection theory the characteristics of organisms 
should be just in that degree the more constant, the more 
useful they are. Hence there is here a serious discrepancy 
between theory and fact. Darwin himself felt the force of 


this objection and met it in a manner not at all acceptable \ 


to the ultra-Darwinians, that is the strict selectionists of 
post-Darwinian times. He admitted that these trivial, ap- 
parently non-useful, but constant specific characters could 
not be explained by natural selection, and must be due to a 
fixation in the species of these characters at one time or 
another through the nature of the organism and the influ- 
ence of extrinsic influences; a true Lamarckian or at least 
anti-Weismannian * explanation. 

This objection to the selection theory based on the ad- 


* Students and readers who have not read Darwin recently, or 
in the light of the controversy between the neo-Darwinians and the 
neo-Lamarckians, that is, between those who disbelieve and those 
who believe in the inheritance of acquired characters, will be sur- 
prised to note on a careful re-reading of the “Origin of Species,” 
with this post-Darwinian sharp distinction in mind, how often Dar- 
win calls on the Lamarckian factors to help his species-forming 
theories out of tight places. Morgan in his “Evolution and Adap- 
tation” points out many cases of this. 


1 ime 


40 DARWINISM TO-DAY. 


mitted existence of indifferent species characters is well stated 
by Conn’ as follows: “But how is it with char- 
Conn’s state- ane : 
mentoftheob- acters that have no utility? It is, of course, a 
faery great achievement to be able to point out the 
trivial charace method by which adaptations have been pro- 
one, duced, but if animals have some characters that 
are not useful, natural selection does not explain them. 
Natural selection can develop useful organs only. The real 
problem which our naturalists are trying 10 solve is not the 
origin of adaptations..simply.but-the-ori specres-also. 
Now while many of the characters and organs of animals 
and plants are of utility to the individual there are others 
that appear to be useless. As animals and plants are 
studied, it is found that the different species differ from 
each other by certain definite characters. These distinctive 
peculiarities that distinguish species are called ‘specific 
characters, and this term will be hereafter used in this. 
sense. The explanation of the origin of species must then 
account for the origin of specific characters. Now specific 
characters are frequently trivial in nature. This was long 
ago recognised by Darwin, who saw that the characters by 
which species are distinguished are frequently so trivial as to 
be apparently useless. If, however, we are to explain the 
origin of species we must find an explanation of these trivial 
characters as well as the more important ones. If these 
trivial characters are of no use to their possessors, then 
manifestly the principle of the survival of the fittest does 
not account for them. The fact that species are so com- 
monly separated by characters that seem to be absolutely 
useless has led some of our keenest naturalists to insist that 
the survival of the fittest does not explain the origin of 
species, but explains only the origin of adaptations. At all 
events, it is clear that the problem of the utility of specific 
characters is a very fundamental one to the discussion of the 
principle of survival. 








DARWINISM ATTACKED. 4t 


“We here come to the first parting of the ways between / 
scientists of different schools. On the one hand we find those |_ 
who are so thoroughly convinced of the universality of the 
principle of natural selection that they insist that all specific . 
characters are useful, however useless they may seem. It 
is beyond question that they are led to this belief in the 
utility of all characters, not from observation, but simply 
from their belief in the sufficiency of the law of natural 
selection. They tell us that we know too little of the actual 
life of organisms in nature to enable us to say that any 
given character is not of use; and to make a claim that any- 
thing, no matter how trivial, is useless, is simply to confess 
ignorance. We must acknowledge that many seemingly 
useless organs have been found to have utility as soon as the 
life habits of animals are better understood. Certainly, 
utility has been found more universal than was believed to : 
be possible a quarter of a century ago. The followers of \—~ 
Darwin have given very much attention to this matter. 
They have pointed out many lines of utility hitherto not 
dreamed of. They have considered great multitudes of 
cases of seemingly useless characters, and by a little imagina- 
tion have suggested some use to which they may be adapted. ‘ 
If one reads the recent works of Wallace, the most promi- 
nent advocate of this position, he will not fail to be im- 
pressed with the fact that utility is much more widely 
applicable as an explanation of seemingly trivial characters 
than might have been thought possible. The position held | 
by this writer is, that inasmuch as the law of natural 
selection is a universal force which all admit, while all other 
forces of evolution are yet in dispute, and inasmuch as many | 
seemingly useless organs have been shown to be of use, it is | 
perfectly legitimate to claim that when we come to under- 
stand them, we shall find that all characters are of value, and ; 
that the principle of survival of the fittest has been concerned: . 
in the development of them all. If this is true, the survival 


42 DARWINISM TO-DAY. 


of the fittest explains the origin of species as well as the 
origin of adaptations, since all specific characters are really 
adaptations. 

“But on the other hand, many naturalists think that there 
are specific characters for which we cannot only see no 
utility, but which are demonstrably of no use. A few illus- 
trations will serve to make the matter clearer. Certain in- 
sects are distinguished from each other in accordance with 
whether they possess one or two bristles on the head. Here 
is a character which appears to be constant, and which must 
therefore be explained by any complete theory of the origin 
of species. Can we imagine that the question of whether 
the animal has one or two hairs should ever have been of 
selective value? But if developed by natural selection, this 
character must at some time have been a matter of life and 
death. Again among snails, the shells commonly coil in 
the same direction in the same species, this fact making the 
direction of the coiling of the shell a specific character. But 
clearly this is not a matter of selective value, since living 
among the rest of the individuals will frequently be found 
some with their shells coiled in the opposite direction. 
Again, horses have small horny callosities on their feet. No 
one has suggested any possible use for them, but neverthe- 
less they are present on the feet of all the species of the horse 
family. But the most curious fact is that while the horse has 
them on all four feet, the ass has them on only two. Now, 
upon the principle that utility is universal, it would be neces- 
sary to claim, not only that the presence of four callosities 
has been a matter of selective value in the horse, an ex- 
tremely difficult thing to believe, but also that the presence 
of only two instead of four has been of selective value in the 
ass. This position approaches absurdity. Again, there are 
molluscs characterised by special markings of the shell, 
which markings are constant enough to be specific char- 
acters, and must, of course, be included in any explanation 


DARWINISM ATTACKED, 43 


of the origin of species. But these marks are demonstrably 
of no use, since they are entirely covered by the epidermis 
of the animal when alive, and absolutely invisible. Again, 
some birds have slight differences in colour markings which 
‘separate species. Now these differences may perhaps be re- 
garded as of use as protective or as recognition marks. 
But in some cases the colour markings are entirely con- 
cealed by other feathers and, being invisible, can be of no 
possible utility. It is hardly possible for one, unless he has 
decided previously to accept the all-sufficiency of natural 
selection, to believe that there can be any utility in the very 
slight differences in the shape of leaves of plants, in the micro- 
scopic markings of the hairs of different species of mammals, 
the exact numbers of the feathers in the tails of birds, the 
peculiar distribution of the veins in the wings of a butter- 
fly, the microscopic markings in the scales on its wings, or 
a host of other similar trivial characters. When it is re- 
membered that the selection principle would force us to 
insist that all of these characters are of value sufficient to 
protect their possessors at the expense of, other individuals 
not possessing them, it is evident that the burden thrown 
upon the principle of survival becomes very great. When 
finally we come to characters of specific nature connected 
with colour markings which are invisible when the animal 
is alive, there is apparently no resource left except to con- 
clude that the principle of survival because of utility does 
not account for everything.” 

It is indeed the general recognition by naturalists of the 
fact of the triviality or indifference of a majority of specific 
‘characters that has led to the recent renewal of the import- 
ance of isolation theories, particularly of geographical 
isolation. The rehabilitation of Moritz Wagner’s theory of 
‘species-forming by migration and isolation is a conspicuous 
feature in present-day evolution discussion. The way in 
which isolation comes to the aid of selection, or even sup- 


a, 


44 DARWINISM TO-DAY. 


plants it in the minds of some, in species-forming is pointed 
out in chapter ix, to which the interested reader may 
Geter: 

But in those cases where the differences or variation 
among individuals may be or obviously are of the character 

The swamping Of useful ones, and where by comparing ex- 
or extinguishing tremes of this variation the life-and-death- 
of favourable va- ‘ ; ME ¢ 
riations by inter- determining worth of this utility might be 
oe conceded, still what chance is there for the 
perpetuation of this advantage? Nageli long ago pointed 
out that the extreme variations, that is, the rare variations, 
would in almost every case be inevitably extinguished by 
interbreeding. If a certain considerable variation occurred 
in one individual of a hundred born, in 20,000 individuals of 
the species 200 would have this worth-while variation. 
Now if the chances of mating are the same for all there 
would be 9,801 parings of individuals not showing the 
variations, 198 pairings between a varying individual and a 
non-varying one, and a single mating between two indi- 
viduals both preserving the considerable variation. In fact 
every rare variation will, as Delage says, be immediately 
effaced by the dilution of the blood of the varying individual 
by that of the great mass of individuals not possessed of the 
particular variation. This inevitable swamping of the ad- 
vantageous variations of individuals has long ago led to the 
practical giving up by Darwinians of any claims to species- 
forming or evolution on the basis of extreme or rare varia- 
tions and to the restriction of the selecting influence to 
masses. The species must be changed through the selection 
of it as a mass or unit rather than through the selection of 
special scattered individuals of it. 

But for the selection of masses of individuals sufficiently 
considerable to avoid the extinguishing of the fortunate 
variations by interbreeding, and to insure a repetition of 
the advantage and an opportunity for its fostering and 


DARWINISMTATTVACKED:, 45 


increase, there is necessary an extraordinary coincidence in 
the appearance of the needed variations in many forms at 
The needed co- the right time. Thatis,a theory based on chance 
incident occur- or accidental phenomena demands after all the 
rence of several i 
variations atone a5SUmption® of the occurrence of phenomena 
pime, of the right kind at the right moment, and 
the persistence of such occurrences through a definite 
time-period. This is too much to assume, too much to ask 
even of those of the true faith, say the antagonists ** ** of 
the selection theory. Kronig *’ makes sport of the selection 
doctrine by having his rather frivolous character, Sabtuch- 
winski, undertake to have made, by a foolish clown, various 
trifling changes in all kinds of industrial products with the 
expectation of bringing them into the market. He is con- 
vinced that he will win a fortune by this, for he says to 
himself that the struggle for supremacy must work out the 
same in the industries as in nature, and in his case with the 
added advantage that the changes effected by even the most 
slender-witted boor must result better than those which are 
the outcome of perfectly blind chance. Indeed, from the 
very heart of the neo-Darwinian ranks come signs of dis- 
may when this objection is faced. Weismann, leader of the 
ultra-selectionists, practically concedes the irrefutability of 
this objection to the Allmacht of selection when he intro- 
duces a statement of his latest theory, that of Germinal 
Selection, by saying :** “Knowing this factor [that of germi- 
nal selection] we remove, it seems to me, the 
Weismann’s ae . 
admission ofthe Patent contradiction of the assumption that the 
Seah aera general fitness of organisms or the adaptations 
necessary to their existence are produced by 
accidental variations—a contradiction which formed a seri- 
ous stumbling-block to the theory of selection.” And the 
formulation of the theory of germinal selection is of itself 
a practical confession on the part of the foremost neo- 
Darwinian. of the inability of natural selection to explain 


46 DARWINISM TO-DAY. 


species-forming without calling to its aid some effective 
factor to control in its beginnings the variation essential 
as the basis of the selective action. 

Pfeffer ** and Wolff ** have been particularly keen and 
severe in their criticism of the selection theory on the basis 
of this objection. And Morgan” in this country has also 
made effective use of this weapon in his destructive con- 
sideration of the Darwinian theories. 

There is an additional point about this difficulty of the 
necessity for a certain regularity or reliability of variation 

penis in order to make a beginning basis for the action / 
coincident ap- Of selection. It is this. Close scrutiny reveals 
LSmhepuinae ie cats necessity often of the occurrence of several 


variations to 
make acertain coincident variations in order to make any one 


eae characteristic positively advantageous. What 
advantage in the way of increased speed is a slight added 
length of leg without a simultaneously added strength of 
musculation; or an increase in size of antlers without a 
simultaneous increase in strength of neck muscles to sup- 
port and manipulate the heavier head? What faint prob- 
ability of the occurrence coincidently of the necessary varia- 
tions (if determined only by chance, that is, the law of prob- 
ability) to produce a gradual perfecting of so complex 
a structure as the vertebrate eye? Or, more, how incon- 
ceivable the coincidences, if variation is purely fortuitous, 
necessary to the simultaneous development of two exactly 
similar eyes: two eyes so intimately associated physio- 
logically that normal sight is a function of both these 
separated organs working perfectly together. Is variation 
to be assumed to be governed by some law of bilateral 
symmetry? But I have shown for many cases ** that in such 
perfectly and fundamentally bilaterally symmetrical animals 
as insects neither the usual Darwinian fluctuating variation 
nor the rarer discontinuous or sport variation is governed 
at all by sucha law. In fact the independence of the varia- 


DARWINISM ATTACKED. 47 


tion phenomena in right and left members of bilaterally 
arranged pairs of organs as wings, antenne, legs, etc., is a 
noticeable fact. This denial of the capacity of the selection 
of fortuitous slight variations to account for coadaptation 
and for the continuous perfecting of complex organs has 
been stated as follows: “It is highly improbable that for the 
steady perfecting of an organ, the variations needed by — 
selection will always appear just at the right time.” Or in 
more expanded form: “It is highly improbable that during 
the modification of a complex organ such as a whole body 
part, or during the gradual perfecting of an adaptive modi- 
fication, the numerous necessary variations will appear suc- 
cessively in such series that a harmonious combination of 
the single variations will be possible.” The -objection cer- 
tainly needs no elaboration. ‘The Darwinian variations ap- 
pear in all directions at all times in slight degrees with no 
determinate direction nor correlation. Selection is to find 
in these variations its only material with which to build up 
to wonderful complexity and perfection of coadaptation 
and correlation of parts ** on a basis of constant advantage, 
such an intricate but harmoniously adjusted compound organ 
as the human eye, in which the failure or imperfectness of a 
single minute part can at any time, during the course of 
development, rob the whole of any advantage whatever to 
the organism possessing: it. 

Wolff ** enlarges on the difficulty of explaining any 
identical structures of the animal body which appear in one 

Difficulty of and the same organism to the number of two 
explaining te- or more. “It cannot be explained,” he says, “by 
peated identical : : 
structures by | S€lection, how the carnivores, for example, can 
selection, have developed through fortuitous yet always 
similar variations, two such structures agreeing in all de- 
tails as the back teeth, which have developed in course of 
time from small skin teeth. That a tooth can develop into 
such an admirable biting organ through chance variation may 


48 DARWINISM TO-DAY. 


be explicable by selection, because we are accustomed to 
postulate thoroughly fortuitous and all-inclusive variation ; 
but that the tooth standing next to it shall have varied al- 
ways in exactly the same way so that the result of its de- 
velopment shall make it identical with the other one, is 
inexplicable by selection on a basis of fortuitous variation, 
but rather indicates that the change of form is ruled by law 
which we do not know. The attempt to discover it is the 
most imperative task for biologists to undertake.” 
Wolff ** follows this argument farther by discussing other 
particular examples, but they are all of the type of the one 
Spencer's pic. JtSt set out. Spencer pictures the situation of 
ture of theinu- the herbivorous animals in a country of in- 
tility of advan- } 
tageinasingle Clement climate and populated by numerous 
ek carnivores. Now those herbivores“vhich have 
the finest hearing will be soonest aware of the approach of 
the tiger, but those with keenest sight or most perfect sense 
of smell will also perceive, as soon, that it is time to flee. Buty 
what advantage over others will the first start in flight give | | 
them? Others less delicately endowed with sense organs 
but swifter of foot will, although starting a little later, have 
as good a chance to escape because of their more rapid run- 
ning. Later may come snow and terrible cold. Those in- 
dividuals best endowed with sense-organs or swiftest of foot 
will not necessarily be the most enduring or the best 
equipped with instincts to find shelter. The climate may 
decimate those which selection on the basis of special senses 
or speed has saved. But after the cold may come the sum- 
mer drought. Those most heavily furred or warmest- 
blooded which have successfully endured the low temperature 
and snow and ice of winter should be the first to suffer from 
the attacks of sun and drought and lack of food in the 
summer. Thus no individual has, because of advantage in 
vany one character, any real and complete superiority which 
yf | guarantees it success in all the phases of the struggle for 
Te 


| 


DARWINISM ATTACKED, 49 


existence: the advantages are scattered and compensated 
by disadvantages.” 

In connection with the objection stated in the preceding 
paragraphs is that specially pressed by Wolff, although long 

Numerous use- 280 strongly stated by Mivart,*’ and one that 
ful characteris- has long appealed strongly to me particularly in 
tics useful only yr ; ye 
in highly per- COnnection with the study of the utility of 
fected state. = colour and pattern among insects. This ob- 
jection is, that numerous useful characteristics or adapta- 
tions of organisms are useful only in a highly perfected 
state, often involving a complex and considerable structural 
development of old (then much modified) or quite new parts, 
and hence could not have arisen by gradual modification by 
the selection of slight variations. Darwin himself says that 
if a single complex organ can be referred to whose full de- 
velopment cannot possibly be explained through numerous 
small successive modifications, then his theory must indubi- 
tably fall. For example, the electric organ of the torpedoes, 
the brood-sacks or cells on the back of Pipa dorsigera, the 
chameleon’s tongue, and many other organs can be recalled 
which could not possibly exercise their particular advanta- 
geous function in an undeveloped and beginning state. In 
my own eyes has for long stood the familiar case of the 
mimicry of our common American monarch butterfly, 

Mimicry of Anosia plexippus, by the viceroy butterfly, 
Anosia by Basilarchia archippus. The viceroy belongs to a 
josh ie group of species in which the prevailing (almost 
certainly the ancestral) colour and pattern are white and 
black (or iridescent purplish and bluish) arranged as a broad 
white continuous transversal bar across both fore and hind 
wings, on a black (to purplish) ground. The colour and 
pattern of Anosia are radically different; brick-red ground, 
black longitudinal lines following the veins and small white 
spots in an irregular black submarginal band. Examine the 
viceroy butterfly. You find no suggestion of typical Basi- 


50 DARWINISM TO-DAY. 


larchia type of colour and pattern; on the contrary, you 
find an extraordinarily faithful imitation (duplication) of 
Anosia’s colour and pattern. Only in a narrow black trans- 
versal streak across the outer disc of each hind wing is there 
any divergence in the viceroy from the Anosia pattern. 
Now Anosia is distasteful to birds; after a few experiments 
with Anosia a bird recognising this ill-tasting morsel in its 
conspicuous red-brown livery leaves the monarchs alone. Not 
only monarchs, however, but also viceroys, which are to all 
external seeming only slightly smaller monarchs. The viceroy 
is, however, not distasteful; it would be a welcome bonne 
bouche to any bird that could distinguish it. But thanks to 
its perfectly mimicking colour-pattern it wings its deceitful 
way unmolested. There is huge usefulness here, and selec- 
tion can well be the steadfast maintainer of the viceroy’s 
dissimulation. But of what avail for this purpose of deceit 
was the first tiny tinge or fleck of red-brown on the staring 
black and white wings of the ancestral viceroy? How can 
one possibly conceive of an attainment of this identity of 
pattern between mimicker and mimicked by selection on a 
basis of life-or-death-determining advantage of slight chance 
appearances of brown or reddish flecks or tinges in suc- 
cessive viceroys? “Not until practically full development of 
the mimicry pattern existed can this pattern have worked its 
advantage. It is, indeed, a different matter with many, per- 
haps most, cases of general or special protective resemblance. 
A little green, a little brown could obviously help the insect 
living in green foliage, or on the ground. Every change of 
tinge toward the general environing colour is worth while; it 
helps melt the insect into its inanimate surroundings. But 
with mimicry it must be the whole thing or nothing; or at 
least near enough to the whole thing to pass for it. Wolff 
puts the objection about as follows: There are compound 
organs and complex adaptations, whose complication (he 
would better say, whose advantage due to complication) can 


DARWINISM ATTACKED. 51 


only be reached by a leap, while the selection theory pre-’ 
supposes slight gradual stages of complication. 
Wolff *® expresses another phase of this objection by re- 
ferring to a few of many cases of complex relations between | 
Difficulty of entirely distinct organs in the body, which 
explaining com- relations constitute some of the most important 
soaadeaay functions of the body. For the successful 
parts by selec- establishment of these relations it has been 
tion. : 
necessary, as Wolff expresses it, “that for each 
advance in development or complexity of one definite pecu- 
liarity in an organ there must appear corresponding and 
exact definite advance in development or complexity of a 
peculiarity in another entirely distinct organ.” Wolff’s first 
example is the relationship existing between the muscles 
and nerves of the higher animals. The intimate, delicate, 
and precise character of the relations between the nerve-end- 
ings and the muscle cells, to be explicable by selection of 
fortuitous variations, must have required coincident varia- 
tions both in structure and functions of each muscle cell and 
each nerve-ending that are impossible to conceive of. “It 
might be,’ says Wolff, “possible to picture the gradual 
development of the relations between one muscle cell and 
one nerve-ending on the basis of a selection among infinitely 
fortuitous variations, but that such variation shall occur 
coincidently in time and character in hundreds or thousands 
of cases in one organism is inconceivable.” 
In the case of organs whose functions are regulated from 
a common centre, the development of centre and of organs 
must have gone on coincidently and could not have been 
independent. The development of the eye is useless if 
the development of the optic centre did not go hand in 
hand with it. Without the one the other has no reason, 
no significance, therefore selection could have brought 
neither to its proper development independently. The 
coincident appearance, however, of organ and centre can 


52 DARWINISM TO-DAY. 


be explained by the selection theory only when there is 
postulated a definite degree of complexity of the fortu- 
itously appearing slight variations, that is, when this 
theory is in condition to assume that which would be a 
denial in terms that variations are wholly fortuitous. 
Wolff goes on to give certain examples of such complex 
relations which involve a dependence of the use upon an 
instinct, as the performance by the queen honey-bee of her 
particular functions in the hive, etc. 

“Out of this discussion,’ says Wolff, “finally we must 
postulate that structures which are to be explained by the 
selection theory must possess at the least two certain charac- 
teristics. Such a structure, namely, must occur but once 
in an organism [that is, must not be a serially or bilaterally 
repeated organ, nor indeed appear in any condition of plural 
number]; further, it must not stand in any necessary relation 
to any other part of the same organism, that is, in a relation 
which one can interpret as a relation not existing from 
the beginning, therefore one which must be looked on as an 
acquired relation. But if we survey the whole animal king- 
dom it will be very difficult for us to find any structures 
which satisfy both these requirements. It might be possible 
to find some which perhaps seem to satisfy the second re- 
quirement, but with regard to the first requirement I may 
declare,’ says Wolff, “that there is scarcely a single structure 
which fulfils it. Symmetry alone, which rules almost all 
organisms, makes organs which appear in the singular num- 
ber rarities, and even such as the pancreas, etc., are com- 
posed of many finer structures, which are homodynamous 
among themselves. When we find two similar organs in 
different animal groups we seek for a causal explanation of 
this similarity and find it in common ancestry. It is absurd 
to seek a causal explanation for the origin of homologous 
structures and yet postulate a purely chance or fortuitous — 
explanation for the origin of homodynamous structures.” » 


DARWINISM ATTACKED. 53 


Another objection which the study of the utility of col- 
our and pattern *‘ also has impressed upon me is that of the 

Objection based carrying too far of certain lines of modification. 
on over-speciali- Classic examples are the fatal over-development - 
veers of the antlers of the extinct Irish stag, the un- - 
wieldiness of the giant Cretaceous reptiles, the intimate 
identity of the halves of bilaterally symmetrical animals. 
Let me call attention to an overdone case of “protective 
resemblance’ among the insects. It is that of the famous 
Kallimas, the dead-leaf butterflies of the Malayan and gen- 
eral south tropical regions. These butterflies (there are 
several species which show the marvellous imitation) have 
the under sides of both fore and hind wings so coloured and 
streaked that when apposed over the back in the manner 
common to butterflies at rest, the four wings combine to 

Kallima, the resemble with absurd fidelity a dead leaf still 
dezi-leaf butter- attached by a short petiole to the twig or branch. 
ah I say absurd, for it seems to me the resemblance 
is over-refined. Here for safety’s sake it is no question of 
mimicking some one particular kind of other organism or 
inanimate thing in Nature which birds do not molest. It is 
simply to produce the effect of a dead leaf; any dead leaf; 
a brown, withering leaf on a branch. Leaf-shape and gen- 
eral dead-leaf colour scheme are necessary for this illusion, 
But are these following things necessary? namely, an 
extraordinarily faithful representation of mid-rib and lateral 
veins even to faint microscopically-tapering vein tips; a 
perfect short petiole produced by the apposed “‘tails’”’ of the 
hind wings; a concealment of the head of the butterfly so 
that it shall not mar the outlines of the lateral margin of the 
leaf; and, finally, delicate little flecks of purplish or yellow- 
ish brown to mimic spots of decay and fungus-attacked spots 
in the leaf (!) and, as culmination, a tiny circular clear 
spot in the fore wings (terminal part of the leaf). which shall 
represent a worm-eaten hole, or a piercing of the dry leaf 


54 DARWINISM TO-DAY. 


by flying splinter, or the complete decay of a little spot due 
to fungus growth! A general and sufficient seeming of a 
dead leaf, object of no bird’s active interest, yes, but not a 
dead leaf modelled with the fidelity of the wax-workers in 
the modern natural history museums. When natural selec- 
tion had got Kallima along to that highly desirable stage 
when it was so like a dead leaf in general seeming that 
every bird sweeping by saw it only as a brown leaf clinging 
precariously to a half-stripped branch, it was natural 
selection’s bounden duty, in conformance with its obligations 
to its makers, to stop the further modelling of Kallima and 
just hold it up to its hardly won advantage. But what 
happens? Kallima continues its way, specifically and ab- 
surdly, dead-leafwards, until to-day it is a much too fragile 
thing to be otherwise than very gingerly handled by its 
rather anxious foster-parents, the neo-Darwinian selec- 
tionists. 

An objection which was long ago pointed out, and which 
has been emphasised strongly by some biologists and almost 

overlooked by others, is that of the incom- 
a ar patibility of the results concerning the age of 
selection oppor- life on this earth as propounded by physicists 
eral! todoits and astronomers with the demand made by the 

theory of descent. This objection of the lack 
of time for the production of the hosts of kinds of plants 
and animals through the slow workings of natural selection 
was brought forward against Darwin from the very begin- 
ning and has never been given up. De Vries,”* for example, 
in a recent paper, refers to it as follows: 

“The deductions made by Lord Kelvin and others from the 
central heat of the earth, from the rate of the production of 
the calcareous deposits, from the increase in the amount of 
salt in the water of the seas, and from various other sources, 
indicate an age for the inhabitable surface of the earth of 
some millions of years only. The most probable estimates 


DARWINISM ATTACKED. 55 


lie between twenty and forty millions of years. The evolu- 
tionists of the gradual line, however, have supposed many 
thousands of millions of years to be the smallest amount 
that would account for the whole range of evolution, from 
the very beginning until the appearance of mankind. This 
large discrepancy has always been a source of doubt and a 
weapon in the hands of opponents of the evolutionary idea, 
and it is especially in this country that much good work has 
been done to overcome this difficulty. The theory of descent 
had to be remoulded. On this point conviction has grown 
in America during the last decades with increasing rapidity.” 

However (according to a newspaper clipping), Professor 
Lankester,” a present-day Darwinian champion, in the 

Ration aen ee of an interesting outline of the advance- 
sible answerto ment of science in the past twenty-five years 
the objection, = hich he gave at the opening meeting of the 
British Association at York recently (September, 1906) 
again raised the question of the age of the earth. Refer- 
ring to the discovery of radium as one far exceeding in 
importance all other modern scientific discoveries he said 
that if the sun contained a fraction of one per cent. of radium, 
this radium would account for and make good the heat that 
is annually lost by the sun. “This is a tremendous fact, 
upsetting all calculations of physicists as to duration in past 
and future of the sun’s heat and the temperature of the 
earth’s surface. The geologists and the biologists have long 
contended that some thousand million years must have 
passed during which the earth’s surface has presented ap- 
proximately the same conditions of temperature as at pres- 
ent, in order to allow time for the evolution of living things 
and the formation of aqueous deposits of the earth’s crust. 
The physicists,’ contended Professor Lankester, ‘notably 
Professor Tait and Lord Kelvin, refused to allow more than 
ten million years (which they have subsequently increased 
to a hundred million, basing the estimate on the rate of 


56 DARWINISM TO-DAY. 


cooling of a sphere of the size and composition of the earth). 
They have assumed that its material is self-cooling. But 
as Huxley pointed out, mathematics will not give a true 
result when applied to erroneous data. It has now, within 
the last five years, become evident that the earth’s material 
is not self-cooling, but on the contrary self-heating, and 
away go the restrictions imposed by physicists on geological 
time. They are now willing to give us not merely a thou- 
sand million years, but as many more as we want.” 

In this connection should be mentioned the position taken 
by Ammon *’ and others who argue that the real effect or 

Claim that se. result of natural selection is to preserve the 
lection hinders type at the expense of the variants, which would 
rather than pro- ~ : 
motes species- Make it a retarder rather than accelerator of 
change, species-change. Bumpus’s ** observations on, 
and conclusions concerning, his storm-beaten English spar- 
rows is an example of what Ammon claims must be the 
real result of selection. Bumpus, in statistical studies of the 
variation of two animal species introduced from Europe into 
the United States, viz., the English sparrow and the peri- 
winkle, Littorina littorea, shows that the eggs of the sparrow 
and the periwinkles themselves are much more variable in 

Banna ote America than in their native regions, and the au- 
servationson thor attributes this increased variability to their 
ce tony “presumable emancipation from many of the re- 
straining influences of natural selection.” In the case of the 
English sparrows, also, Bumpus believes himself able to 
show on a basis of the examination of 136 birds brought 
in wounded or stunned after a severe storm of snow, rain, 
and sleet (Feb. 1, 1898), that the sixty-four birds that 
perished (seventy-two revived), “perished not through acci- 
dent, but because they were physically disqualified, and that 
the birds which survived, survived because they possessed 
certain physical characters. These characters enabled them 
to withstand the intensity of this particular phase of selective 


DARWINISM ATTACKED. 57 


elimination and distinguish them from their more unfortu- 
nate companions.” The fortunate characters were mas- 
culinity, shortness of body, lightness, longer humerus, longer 
femur, longer tibio-tarsus, longer sternum, greater brain 
capacity. But more important for survival than favourable 
variations was the fact of approach to the species type or 
mode of variability. The extreme variants perished. 
“The process of selective elimination is most severe with ex- 
tremely variable individuals, no matter in what directions the 
variations may occur. It is quite as dangerous to be con- 
spicuously above a certain standard of organic excellence 
as it is to be conspicuously below the standard. It is the 
type that nature favours.” 


APPENDIX. 


* For a fairly complete bibliography, with excellent abstracts, of 
all important critical discussions of Darwinism since 1895, see 
L’Année Biologique (ed. Y. Delage), 1895-1903; for good bibliog- 
raphy also see Zoologischer Jahresbericht, issued annually. See 
also discussions and notes in such journals as Natural Science, Bio- 
logisches Centralblatt, Nature, Science, American Naturalist, etc. 

?Von Kolliker, A., “Uber die Darwin’sche Schopfungstheorie,” 
Zeitsch. f. wiss. Zool., Vol. XIV, pp. 174-186, 1864. 

® Korschinsky, S., “Heterogenesis und Evolution,’ Naturw. Wo- 
chenschrift, Vol. XIV, pp. 273-278, 1899. 

* Morgan, T. H., “Evolution and Adaptation,’ 1903. A vigorous 
anti-Darwinian argument, somewhat sophisticated in its lawyer- 
like handling of Darwin’s own words, but keen and trenchant in 
its exposure of the weaknesses of the selection theories as species- 
forming explanations. It is also a brief for de Vries’s theory of 
species-forming by mutation. (See chap. xi of this book.) 

5 “See Osborn, H. F., “Biol. Lectures,” Wood’s Holl Lab., 1894, 
pp. 79-100, for suggestive plea for the recognition of “the unknown 
factors of evolution.” 

®° The subject of variation, an absolutely fundamental one in any 
consideration of the factors and mechanism of organic evolution, has 
a very large literature pertaining to it which the 
serious student of evolution must make considerable 
acquaintance with at the very outset. Of this litera- 
ture the following books and papers may be suggested to serve as 


Books and pa- 
pers on variation, 


58 DARWINISM TO-DAY. 


a means of introduction to the subject, not alone in its broad out- 
lines, but in its extensive ramifications of relation to other evolution 
problems. Some of these books and papers include extended biblio- 
graphic lists sufficient to enable one to follow up the subject in any 
of its special phases. 

Darwin, Chas., ‘“The Origin of Species,” 1859. 

Darwin, Chas., “The Variation of Animals and Plants under 
Domestication” (Amer. ed.), 1868. 

Wallace, A. R., “Darwinism,” chaps. iii and iv, 1891. 

Allen, J. A., “On the Mammals and Winter Birds of East Florida,” 
Bull. Mus. Comp. Zool., Il, pp. 161-450, Plates IV-VIII, 1871. 

Galton, F., “Natural Inheritance,” 1880. 

Bateson, W., ‘Materials for the Study of Variation,” 1894. 

Duncker, G., “Die Methode der Variationsstatistik,” Archiv f. 
Entwick. Mech., Vol. VIII, pp. 112-183, 1899. (Full bibliography.) 

Rosa, D., “La riduzione progressiva della variabilita i suoi rap- 
porti coll’ esstinzione e coll’ origine delle specie,” 1899. 

Conn, H. W., “The Method of Evolution,” chap. iv, 1900. 

Davenport, C. B., ‘““A History of the Development of the Quan- 
titative Study of Variation,” Science, N. S., Vol. XII, pp. 864-870, 
1900. 

De Vries, H., “Die Mutationstheorie,’ Vol. I, pp. 7-150, pp. 
412-648, I9OI. 

Ewart, J. C., “Variation; Germinal and Environmental,” Trans. 
Roy. Dublin Soc., Ser. II, Vol. VII, pp. 353-378, 1901. 

Vernon, H. M., “Variation in Animals and Plants,” 1903. 

Delage, Y., “L’Hérédité,” pp. 283-310, pp. 826-843, 2d ed., 1903. 

Davenport, C. B., “Statistical Methods in the Study of Varia- 
tion,’ 2d ed., 1904. (Full bibliography.) 

Kellogg and Bell, “Studies of Variation in Insects,’ Proc. 
Wash. Acad. Sct., Vol. VI, pp. 203-332, 1904. 

Lotsy, J. P., “Vorlesungen tuber Descendenztheorien,” Vol. I, 
chap. ix, 19006. 

Biometrika, tgo1-1906. A journal devoted chiefly to the sta- 
tistical study of variation. 

"See Kellogg, “Variation in Parthenogenetic Insects,’ Science, 
N. S., Vol. XXIV, pp, 695-699, 1906, in which it is shown that the 

Cases of marked Parthenogenetically produced drone honey-bees vary 
variation in par- much more than do the workers which are of bi- 
thenogenetic ani- sexual parentage, and that parthenogenetically pro- 
mals. duced plant-lice (Aphidids) vary as markedly as 
insects ‘of bisexual parentage. See also Warren, Proc. Roy. Soc., 
Vol. LXV, 1899, in which the variation in parthenogenetic varia- 
tions of Daphnia magna is shown to be little, if any, smaller than 


9 


DARWINISM ATTACKED. 59 


in sexually produced generations; also, Biometrika, Vol. I, pp. 129- 
154, 1902, in which Warren shows the variation in parthenogenetic 
series of the plant-louse Hyalopterus trirhodus to be as large as 
the variability exhibited in sexual forms. 

See also Haycrait, J. B., “The Role of Sex,” Nat. Science, Vol. 
VII, pp. 245-250, 342-344, 1895, in which paper is presented an ingen- 
ious argument to show that sexual reproduction tends not merely not 
to increase variation but to decrease it: “the convergence to the mean 
is, then, a result of sexual reproduction: it may be termed the role 
of sex, and one indeed of no secondary order. The tendency con- 
stantly to vary is a property inherent in protoplasm, yet often for 
long periods of time the environment may be the same. In order 
that a species may continue to live in such a constant environment, 
the effects of variation must be checked. Sexual multiplication, a 
conservative function, antagonises the progressive tendency of varia- 
tion.” | 

Other naturalists have also held strongly to this view of the role 
of amphimixis. See Bailey, L. H., “The Plant Individual in the 
Light of Evolution,” address before the Biological Society of Wash- 
ington, January 12, 1895, Science, N. S., Vol. I, p. 281, 1895, in which 
paper the author points out the importance of a clear recognition 
of the tremendous possibilities and actuality of asexual variation 
in plants. 

In a paper by Winslow and Rogers (Science, N..S., Vol. XXI., 
p. 486, 1905), referring to the classification of bacteria, there is the 
following statement: “Since the swamping of minor differences by 
‘sexual reproduction is absent from bacteria, every inheritable 
variation is maintained, and instead of true species, we find an infi- 
nite series of minutely differing but constant races. The only prac- 
tical method of handling and systematising these, is to establish cer- 
tain fairly distinct groups and types about’ which the individual 
variations may be grouped.” 

* By using a large series of individuals, and carefully tabulating 
the noted conditions of variation of one or more parts, using, pref- 

uae erably, attributes whose variability is capable of being 

Variation ac- mathematically expressed, such as dimensions, num- 
cording to the law : 
of probabilities, bers of spines, or spots, etc., many students have 

shown that these variations seem to occur in most 
‘cases according to the law of probabilities, and that a curve plotted 
so as to express graphically the actual conditions of variation for a 
given character would be nearly identical with the curve that could 
be plotted so as to express what variation would exist in the given 
case if this variation occurred exactly according to the laws of 
chance. This means that in a thousand individuals collected at 


60 DARWINISM TO-DAY. 


random and examined for variation in any character, say total 
length of body, not only would there be found a larger number of 
individuals of medium length than of any other length between the 
two extremes, represented by the longest and shortest individuals, 
but that the various lengths between the mean and the longest and 
between the mean and the shortest, would be represented by groups. 
of individuals regularly decreasing in number as the length in- 
creased or decreased on either side of the mean, but of equal number 
if compared at equal amounts of difference away from the mean. 
The curve expressing graphically the law of probabilities or, 
better, the frequency of error, is determined by the formula for this: 
frequency deduced originally by Gauss at the beginning of the last 
century. It would lead us too far afield to reproduce here the 
mathematical proof of the formula or method of its determination,. 
but Vernon’s excellent concrete illustration of how such a formula 
could be deduced directly from a study of biologic variation 
may be quoted. ‘‘Supposing,” says Vernon in “Variation in Animals 
and Plants,’ pp. 11 and 12, 1903, “a group of developing organisms 
be taken, of which the growth can be affected in a favourable or an 
unfavourable manner by their surroundings. Let us suppose that 
there are twenty different agencies, each of which would produce 
an equal, favourable effect on growth, and twenty which would pro- 
duce just as great an effect in the opposite direction. Suppose, also,. 
that each organism is subjected to only half of these forty different 
agencies; then it would follow, according to the laws of chance, 
that a larger number of the organisms would be acted upon by 10 
favourable and 10 unfavourable agencies, than by any other com- 
bination; i.e, they would, on our hypothesis, remain absolutely 
unaffected in their growth. A somewhat smaller number would be 
acted upon by 11 favourable and 9 unfavourable agencies, or on the 
whole, would have their growth slightly increased. A still smaller 
proportion would be acted on by 12 favourable and 8 unfavourable 
agencies, or would have their growth rather more increased. Finally, 
the number of organisms acted on by 20 favourable and o unfa- 
vourable agencies would be extraordinarily small, but in this case the 
effect on growth would be extremely large. Similar relationships, 
only in the reverse direction, would of course be found in those 
cases in which the number of unfavourable agencies exceeded the 
number of favourable. If desired, the proportional numbers of organ- 
isms acted on by all the different combinations of agencies may be 
readily determined by expanding the binomial (% + %)’*. It 
is found, for instance, that for each single time the organisms are 
acted on by the whole 20 favourable agencies, they are acted on 190 
times by 18 favourable and 2 unfavourable; 15,504 times by 15 


DARWINISM ATTACKED. 61 


favourable and 5 unfavourable; and no less than 184,756 times by 
10 favourable and 10 unfavourable. Let us consider that the organ- 
isms acted on by 20 favourable and o unfavourable agencies have 
their size increased 20 per cent.; those acted on by 15 favourable 
and 5 unfavourable by 15 — 5 = Io per cent.; and so on. If now 
these percentage increments and decrements be plotted out at equal 
distances on a base line, and ordinates corresponding to the theo- 
retical frequencies erected from each, then by joining these ordinates 
we shall obtain a curve which is practically identical in form with 
the probability curve of the law of frequency of error. Thus, by a 
simple arithmetical method, we obtain a series approximating more 
and more closely to the probability curve, the greater the number 
of times the expression (% + ¥%) is expanded. Expanded 20 
times, the average error is less than .5 per cent., and for a greater 
number of times it becomes rapidly smaller and smaller.” 
This discovery and formulation of the law of individual varia- 
tion—namely, that such variation occurs according to the law of 
probabilities—was first made by the Belgian anthro- 
Pikes aay pologist, Quetelet (‘Lettres sur la théorie des Proba- 
ation according _bilités,” Brussels, 1846), on a basis of the examina- 
to the law of tion of the height and chest measurements of soldiers. 
chance. It was later elaborately confirmed by Francis Galton 
(numerous papers and the book, “Natural Inheritance,’ 1870-1890), 
by quantitative determinations of the height, weight, span of arms, 
breathing capacity, strength of pull, strength of squeeze, swiftness 
of blow, and keenness of sight in men and women. It has been 
most illuminatingly discussed by Karl Pearson in “The Chances of 
Death, and other Studies in Evolution,” 2 vols., 1897. Since then 
the recognised necessity of a more thorough study and understand- 
ing of variation, as the indispensable foundation of species-forming 
has led to a large development of the statistical and mathematical 
study of variation, under the name of biometry, a study largely due 
to the initiative and genius of the English mathematician and natural 
philosopher, Karl Pearson (numerous papers from 1894 to present). 
Most of the methods and formule for determining precise mathe- 
matical expression of variation conditions have been devised by him. 
These methods and formule permit of an actual mathematical com- 
parison of variation among various parts in one species (immensely 
enlarging our definite knowledge of structural correlations), or 
among similar or wholly different parts in various species. With 
the statistical facts or data of variation thus put into precise mathe- 
matical expression, these expressions may be submitted to a deal 
of independent mathematical treatment; rather bewildering, it must 
‘be confessed, to most biologists, but presented by the biometricians 


62 DARWINISM TO-DAY. 


as the first step toward making biology, in part, at least, an exact 
science. But there is no question at all that the statistical and 
quantitative study of variation, and the use of authoritatively 
deduced mathematical expressions (and the graphic representation 
of these by plotted frequency curves, polygons, etc.), have immensely 
advanced our understanding of variation conditions, and given us 
definiteness and concreteness in a fundamental field of evolution 
study, where before were a mass of uncoordinated data and a haze 
of loose generalising. 

* Bateson, Wm., “Materials for the Study of Variation,” 1894. 

7° See Kellogg and Bell, “Studies of Variation in Insects,” Proc. 
Wash. Acad. Sci., Vol. VI, pp. 203-332, 1904, in which are discussed. 
(pp. 257-273) variation conditions existing in the lady- 
Re doh bird beetle, Hippodanua convergens. ‘The variations 

in the number and character of the elytral pattern 
(small black spots on a brown ground) noted in a thousand speci- 
mens examined, were such that eighty-four “aberrations,” or pat- 
tern-variates, could be distinguished and described, and yet, an 
intensity of scrutiny demanding the use of a lens was necessary to 
distinguish properly these varying types. Such a scrutiny, needless 
to say, will never be given these beetles by bird or lizard, the active 
agents representing natural selection, as far as pattern is to be 
tested. Nevertheless, these pattern variations, if not so completely 
connected by gradatory steps, would be exactly the characters on 
which several Hippodamia species would be based, for they range all 
the way from no spots to eighteen spots, although twelve is the 
species character of convergens. 

** Romanes discusses this subject of the indifference, or triviality, 
of many specific characters at some length in chap. vii of his “Dar- 
win and After Darwin,” II, “Post-Darwinian Questions,” “Heredity 
and Utility,” 1895. 

*? Conn, H. W., “Method of Evolution,” pp. 78-83, 1900. 

** Nageli, Carl, ““Mechanisch-physiologische Theorie der Abstam- 
mungslehre,” 1884. Nageli, an eminent botanist, formulated many 

Nageli's seven Years ago the following famous seven objections to 
objections to spe- the natural selection theory of species-forming (pp. 
cies-forming by 289-290) : 
selection, “Ich hebe folgende sieben Gesichtspunkte hervor, 
welche uns die Abstammung durch Zuchtwahl unannehmbar machen: 

“1. Beztiglich der allgemeinen Bedeutung der Selectionstheorie 
ist die unbestimmte Wirkung unbestimmter Ursachen und die dem 
Zufall allzusehr wiberlassene Entscheidung durch die nattirliche 
Zuchtwahl unserem naturwissenschaftlichen Bewusstsein weniger 
zusagend. Ferner setzt sich die Selectionstheorie, welche ihrem 


DARWINISM ATTACKED. 63 


Princip gemass nur nach dem erreichten Nutzen einer Erscheinung 
fragt, um dieselbe zu rechtfertigen, in Widerspruch mit der wahren 
und exacten Naturforschung, welche vor allem die bewirkenden Ur- 
sachen der Dinge zu erkennen sucht. 

“2. Die Folgerung von der (ktnstlichen) Rassenbildung auf die 
(naturliche) Varietatenbildung, welche die Grundlage der Selec- 
tionstheorie ausmacht, ist unzuldssig, da beide wesentlich verschie- 
den sind und namentlich sich rticksichtlich der Kreuzung ungleich 
verhalten. Die Varietaten namlich vermischen sich sehr schwer mit 
einander und nehmen kein fremdes Blut in irgend wirksamer Menge 
auf, werden somit auch durch die ihnen gebotene Gelegenheit zur 
Kreuzung nicht verandert; mit diesen Eigenschaften stimmen ihre 
Vorkommensverhaltnisse genau tberein. 

“3. Nttzliche Veranderungen kénnen erst, wenn sie eine bemerk- 
bare Hohe erreicht haben und in zahlreichen Individuen vorhanden 
sind, eine ausgiebige Verdrangung der Mitbewerber bewirken. Da 
sie aber im Anfange durch eine lange Reihe von Generationen jeden- 
falls noch sehr unbedeutend und nach der Selectionstheorie auch nur 
in einer kleinen Zahl von Individuen vertreten sind, so bleibt die 
Verdrangung aus und eine nattirliche Zuchtwahl kommt, da ihr der 
wirksame Hebel mangelt, tiberhaupt nicht zu Stande. 

“4. Die Ernahrungseinflisse, welche die Selectionstheorie voraus- 
setzt, bewirken thatsachlich keine erblichen Veranderungen, und 
wenn sie es thaten, so konnte eine Steigerung der begonnenen Aban- 
derung nicht eintreten, weil die unvermeidliche Kreuzung eine 
nattirliche Zuchtwahl unmoglich machen wtirde. Ferner lasst sich 
aus den unbestimmten, in allen denkbaren Richtungen wirkenden 
Ernahrungseinfltissen der so stetige phylogenetische Fortschritt zu 
einer complicirteren Organisation nicht erklaren. Ebenso wenig 
werden durch dieselben die Erscheinungen der Anpassung verur- 
sacht; dies ergibt sich einerseits aus dem Umstande, dass Gebrauch 
und Nichtgebrauch die Zu- und Abnahme der Organe bedingen, da 
diese Ursache fiir sich vollkommen ausreicht und daher die Mit- 
wirkung einer zweiten andersartigen Ursache ausschliesst,—und 
andrerseits durch den ferneren Umstand, dass Anfange von Organen 
bis zu der Grosse, wo sie in Gebrauch kommen und ihre Nutzlich- 
keit zu erproben vermogen, mangeln, obgleich sie durch die Ernah- 
rungseinfliisse in Menge hervorgebracht werden mussten. 

“se Die Eigenschaften der Organismen missten in Folge der 
naturlichen Zuchtwahl um so constanter sein, je ntitzlicher sie sind, 
und Einrichtungen, die keinen Vortheil gewahren, konnten keine 
Bestandigkeit erlangen. Im Widerspruche hiermit gehoren gewisse. 
rein morphologische, mit Riicksicht auf den Nutzen indifferente . 
Merkmale zu den allerbestandigsten. 


64 DARWINISM TO-DAY. 


“6. Aus der Selectionstheorie, nach welcher von den eintretenden 
richtungslosen Veranderungen bloss die nutzlichen festgehalten wur- 
den, lassen sich weder die Divergenz der Reihen in den organischen 
Reichen, noch die bestehenden Liicken in und zwischen den Reihen 
erklaren, indem vielmehr eine netzformige Anordnung der Sippen 
zu Stande kommen musste. 

‘7 Ebenso widersprechen jener Theorie das Nichtvorhandensein 
der von ihr behaupteten gegenseitigen Anpassung der Bewohner eines 
Landes und die bestehenden Naturalisationen fremder Erzeugnisse. 

“Diese Einwtirfe gegen die Selectionstheorie, die ich hier bloss 
ganz allgemein formulirt habe, sollen im folgenden des Naheren 
begriindet werden.” 

** Wolff, G., “Beitrage zur Kritik der Darwin’schen Lehre,” 1808. 
From this caustic attack on the Darwinian position, I quote as fol- 
lows (pp. 56-57): 

“Wenn wir sagen, die Selektion schafft Zweckmassiges dadurch, 
dass eben nur das Zweckmassige erhalten wird, das andre zu Grunde 

geht, so wird in dieser Fassung das Zweckmassige 

Wolff's attack natiirlich vorausgesetzt, aber nicht sein Zustandekom- 
on the selection- men erklart. Dass Zweckmiassiges iiberhaupt da war, 
ists’ assumption ._ . “ aes 
of the appearance ist im hdchsten Grade unwahrscheinlich und unver- 
at the right time standlich. Mochte auch unter den vielen Variie- 
of the needed rungen manchmal etwas Zweckmiassiges zufallig 
Pelt! Nee vorgekommen sein, so ist die Wahrscheinlichkeit eines 

solchen Eintreffens so gering, dass ich nicht das Recht 
habe, diesen Faktor als einen gegebenen in meine Rechnung ein- 
zusetzen. Diese Wahrscheinlichkeit sucht nun der Darwinismus 
dadurch zu vergrossern, dass er alle mdglichen Falle annimmt, unter 
welchen naturlich auch das Zweckmassige als Spezialfall enthalten 
sein muss. Der Darwinismus sucht also den Treffer sich dadurch 
zu sichern, dass er den ganzen Gltickshafen mit nach Hause nimmt. 

“Um ein Beispiel zu nehmen: es sei von Vorteil, dass die Schna- 
belform entsteht, wie sie beim Kreuzschnabel vorhanden ist. Der 
Darwinismus nimmt an, dass durch gliickliche Variierung ein bezw. 
mehrere oder sogar viele gekreuzten Schnabel auftraten. Sagt nun 
der Gegner: das spontane Auftreten einer Schnabelkreuzung scheint 
mir so unwahrscheinlich, dass ich diese Voraussetzung eben nicht 
zugebe, so antwortet der Darwinist: unter allen m6glichen Schnabel- 
variierungen ist auch der gekreuzte, darf ich alle, so darf ich auch 
diesen voraussetzen; da aber die Variierung, wie die Beobachtung 
lehrt, nach allen Richtungen beliebig wirkt, so sind alle Variierungen 
moglich, folglich darf ich auch jene spezielle voraussetzen. 

“Der Gegner wiirde jetzt vielleicht so erwidern: Gewiss, modglich 
sind alle Variierungen, aber gegeben ist deren doch immer nur eine 


DARWINISM ATTACKED. , 65 


begrenzte Anzahl. Die Zahl aller moglichen Variierungen ist = ©, 
die Zahl der gegebenen ist eine endliche Grosse. Die Wahrschein- 
lichkeit des Eintretens einer speziellen zweckmassigen Variierung 
(in unserm Beispiel der zweckmassigen Schnabelkreuzung) ist End- 
liches dividiert durch Unendliches, d. h. eine Zahl, welche sich der 
Null ohne Ende nahert; mithin ist die Wahrscheinlichkeit, dass 
unter den gegebenen Fallen sich eine gtnstige Variierung befindet, 
so ungeheuer klein, dass nicht die geringste wissenschaftliche Be- 
rechtigung. besteht, den betreffenden Fall vorauszusetzen. Und nun 
wiirde allerdings demjenigen Darwinisten, welchem die Kihnheit 
fehlte, die Zahl der ihm zur Verftigung stehenden Variierungen ein- 
fach = © zu setzen, wohl kaum etwas andres ubrig bleiben, als sich 
darauf zu berufen, dass es eine Sorte von Variierungen giebt, bei 
denen die Zahl der gegebenen Falle gross genug ist, um alle mégli- 
chen zu enthalten, gross genug also, um die Voraussetzung jedes 
einzelnen wissenschaftlich zu rechtfertigen, namlich diejenigen Vari- 
ierungen, welche nur in graduellen Veranderungen bestehen, bei 
denen es sich also nur darum handelt, dass ein Vorhandenes grosser 
oder kleiner wird. Hier ist die Zahl der moglichen Falle gleich 2, 
die der gegebenen ebenfalls, die Wahrscheinlichkeit, sich unter den 
gegebenen zu befinden, ist also fiir jeden der moglichen Falle 
gleich 1.” 

*’ Kronig, ‘Das Dasein Gottes und das Gliick des Menschen,” p. 
109, 1874. 

*® Weismann, Aug., “On Germinal Selection as a Source of Defi- 
nite Variation,” trans. McCormack, p. 3 (preface), 1806. 

*' Pfeffer, Georg, “Die Umwandlung der Arten,” 1894. 

** Wolff, G., “Der gegenwartige Stand des Darwinismus,” 1896; 
also, ““Beitrage zur Kritik der Darwin’schen Lehre,” 1808. 

** Morgan, T. H., “Evolution and Adaptation,” 1903. 

** Kellogg and Bell, “Studies of Variation in Insects,” Proc. 
Wash. Acad. Sci., Vol. VI, pp. 203-332, 1904. The following is 
quoted from pp. 330-332: 

“Insects are bilaterally symmetrical and metameric animals. There 
are thus right and left and fore and aft structural correlations. Do the 
Example of non- variations, continuous and discontinuous, show similar 
correlated varia- bilateral and metameric correlation? Evidence regard- 
bility in bilater- ing this question will be found on many pages in the 
ally repeated present paper, right and left correlation, at least, hav- 
organs, ; : ‘ : : 

ing been considered and briefly discussed in connection 
with almost all of the various cases studied. And the evidence is 
curiously conflicting. For example, in the male black ant in which 
were studied the variations of the venation and number of hooks, a 
close correlation in the variation conditions of right and left wings 


66 DARWINISM TO-DAY. 


exists. On the other hand, in the honey-bee the bilateral correla- 
tion of variation seems surprisingly small (see pp. 214-222). In 
the case of variations in pattern, also, there is no uniformity among 
the various cases studied. In Hippodamia convergens (p. 257 et 
seg.) the two elytra show pattern-variations quite independently ; 
in Diabrotica soror (p. 274 et seq.), on the contrary, there seems 
to be a marked right and left correlation in the elytral pattern- 
variation. In the cases of the variation in number of tibial spines 
on the right and left hind tibiz of locusts (p. 301) and cicadas (p. 
306), we have simply made a brief statement, in each case, of the 
actual conditions of correlation, leaving the reader to draw his own 
conclusions. In the case of the variation in actual and relative 
length of the antennal segments of the scale insect, Ceroputo yucce 
(?) (p. 310), there is a surprising lack of correlation between the 
right and left antenne. 

“We have not attempted to determine the mathematical expression 
(coefficient of correlation) for any of the cases studied. The data 
presented, however, will enable any biometrician, who sees an 
advantage in doing this, to do it. But without checking our results 
by the use of that method there seems, on the whole, to be a sur- 
prising lack of that fine degree of correlation in variation which 
we should expect to find existing, if we believe that the actual 
existing conditions of structure and pattern in these bilaterally sym- 
metrical animals are an expression of the result of the action of 
a rigorous natural selection. If one condition of pattern or structure 
is the most advantageous (of the many conditions which selection 
among a host of fluctuating variations could have established), 
surely this condition ought to be pretty closely similar on both sides 
of the insect. That as much bilateral variety as actually exists, 
in many of the species examined by us, should exist—a variety 
comparable in certain cases even with the degree of variety revealed 
by the comparison of considerable series of individuals—is a state of 
affairs that only confirms us in the belief that these innumerable 
small continuous variations, on which for so long the thorough- 
going selectionists have put their faith as the sufficient bases for 
natural selection’s species-forming work, are clearly not competent 
to serve as such bases. If these ‘continuous’ variations are the foun- 
dation stones of new species, some other agents than selection must 
be found or invoked to build several courses on them, to produce 
some cumulation of them, before natural selection finds them of 
that life-and-death worth which is the prerequisite for her potent 
interference.” 

** Henslow, the botanist, has maintained a constant attitude of 
antagonism to natural selection on the basis of his belief that the 


DARWINISM ATTACKED. | 67 


complex correlations of floral structures cannot possibly be accounted 
for by the natural selection of fortuitous variations. Henslow’s 

ry , observations and ideas are exploited in detail in 

enslow’s an- ae 
tagonismtoselec- two books called, “The Origin of Floral Structures 
tion as explain- through Insect and Other Agencies,” 1895, and 
er of floral corre- “The Origin of Plant Structures by Self-Adaptation 
lations, ; 3 

to the Environment,” 1895. 

?? Wolff, G., “Beitrage zur Kritik der Darwin’schen Lehre,” p. 
6, 1808. 

2° Wolff, G., “Beitrage zur Kritik der Darwin’schen Lehre,” 1808. 
I quote the following, pp. 6-8: 

“Solche Erscheinungen, welche der Erklarung durch die Selek- 
tionstheorie widerstreben, weil sie hier eine gesetzmassige kom- 

plizierte Veranderung der Formen voraussetzen wurde, 

Wolff's objection statt sie zu erklaren, sind aber nicht etwa nur verein- 
to the necessary 7elte Falle, sondern von solchen wird die ganze 
ee Formgestaltung beherrscht, wie z. B. von symme- 
incident varia- trischer Anlage. Auch brauchen wir uns bei dieser 
tion in repeated Betrachtung nicht nur auf solche Gebilde zu _be- 
structures as schranken, die in geringer Mehrheit vorhanden sind, 
ea sealess sondern es giebt ja Gebilde, die in hundert-, ja tau- 

sendfacher Anzahl an einem und demselben Or- 
ganismus sich finden, wie Schuppen, Haare, Federn. Betrachten 
wir z. B. gerade die Federn. Wie viel Millionen Variierungen 
musste eine Reptilienschuppe durchmachen, bis sie sich in eine 
Feder verwandelt hatte, vollends noch in ein so kompliziertes Gebilde 
wie z. B. die Schwanzfeder des Pfaues. Aber dies ware immer 
noch nach der Selektionstheorie erklarlich. Nicht erklarlich dage- 
gen ware, dass die anderen Schwanzfedern immer gleichzeitig 
dieselben Variierungen durchmachten. Ein Gesetz, welches ein 
einheitliches Variieren dieser Hautgebilde vorschreibt, giebt es 
nicht, denn es variieren ja nicht alle gleich. Es entstehen viele 
gleiche Flaumfedern, viele gleiche Schwanzfedern etc., an einigen 
Stellen bleiben die Schuppen sogar erhalten, namlich an den hinteren 
Extremitaten. 

“Wir koénnen noch weiter gehen. Eine Masse von einzelnen Zel- 
len musste bei den verschiedenen Differenzierungen, bei Entstehung 
des Darms, des Nervensystems, der Muskulatur etc. in ganz genau 
der gleichen Weise variieren. Wenn wir hier die Selektionstheorie 
zur Erklarung herbeiziehen wollen, so ist die Kompliziertheit des 
einzelnen Variierungsinkrementes so gross, dass damit die ganze 
weitere Erklarung tberflissig wird. 

“Interessant sind ferner solche homodynamen Gebilde, die nicht 
zu gleicher Zeit auftreten, wie der dritte halbzirkelformige Kanal 


68 DARWINISM TO-DAY. 


im Gehororgan der Wirbeltiere, welcher bekanntlich erst in der 
Klasse der Fische auftritt. Dieser dritte Kanal ist den beiden 
andern voOllig gleich, hat Crista, Ampulle, Macula etc., ist aber 
spater entstanden; die namlichen zufalligen Variierungen, die 
stattfanden bei der Entstehung der beiden ersten Kanale, mussten 
viele Generationen spater ganz genau in derselben Art sich wieder- 
holen! Dass diese Variierungen wieder auftreten, dies erklart die 
Darwinsche Lehre nicht; denn die Selektion kann ja keinen Ein- 
fluss auf die Variierung austben. 

“Aehnlich sind die Resultate der Kowalevskyschen Untersuch- 
tngen uber fossile Huftiere zu betrachten, welche sich auf die im 
Lauf der phylogenetischen Entwicklung stattgehabten Umwand- 
lungen des Extremitatenskelettes dieser Tiere beziehen. Hier kann 
bekanntlich eine allmahlich eintretende Verringerung der Anzahl 
der Metatarsal- und Metakarpalknochen sowie der Phalangen 
verfolgt werden. Diese Verringerung tritt zuerst an den hintern, 
erst spater an den vordern Extremitaten auf!” 

** A moth, Phryganidia californica, whose larve live abundantly 
on the oak trees in California, shows very clearly how a conspicuous 

Example of mal- disadvantage does not seem to interfere much with 
adaptation in egg- Successful life; for the “success” of this moth is only 
laying habit of too well proved by the serious injuries which it pro- 
Phryganidia cali- quces, because of its great numbers, on the beautiful 
fornica, tte : 

trees it infests. For several years the live-oaks and 
white oaks of the Santa Clara Valley were defoliated to a dangerous 
extent. The life history of the moth is told in detail in “The 
Californian Phryganidian,” by Kellogg and Jack, Proc. Cal. Acad. 
Sci., Ser. 2, Vol. V, pp. 562-570, 1895. From this account I quote the 
following: ‘Although most abundant on the live-oaks (Q. agrifolia), 
the larve attack other oaks. We have found them on Quercus 
lobata, QO. kelloggu, QO. dumosa, and Q. douglas. The live-oaks in 
this vicinity begin to put out new leaves about January 1, but in 
the case of many of the trees badly defoliated by the larve in the 
autumn, new leaves appeared much earlier than the first of Janu- 
ary. The wintering of the insect in a larval condition is only possi- 
ble in the evergreen oaks, and they are thus the natural and usual 
host of the pest. At the time of the hatching of the first of the 
autumn brood of eggs (latter part of November), the leaves of the 
deciduous oaks begin to fall. But, oddly, the eggs were found to 
be deposited on the leaves of both the white oak and Douglas’s oak 
(deciduous oaks), and the larve hatched only to die of starvation. 
By this suicidal means the pest aids in depleting its own numbers. 
The new leaves of the deciduous oaks appear about April 1, before 
_ the eggs for the summer brood of larve are deposited. These eggs, 


* 
4 


DARWINISM ATTACKED. 69 


therefore, can safely be laid on the leaves of these trees, but the 
eggs laid by the fall moths on the foliage of-these trees give up their 
young to certain destruction.” 

25 Mivart, St. G., “On the Genesis of Species,” 1871. 

°° Wolff, G., “Beitrage zur Kritik der Darwin’schen Lehre,” p. 8 
ff., 1808. 

?™In Piepers, M. C., “Mimikry, Selektion und Darwinismus,” 
1903, the author strongly antagonises the Darwinian explanation 

Picpers'a an, of protective warning and mimicking colour patterns. 
tagonism to selec- Piepers claims to show (1) that the so-called mimicry 
tion explanation is a phenomenon or appearance whose biological 
of colour and pat- value is greatly over-praised; (2) that the causes: of 
ope at this appearance are not entirely known, yet can in 
most cases be very well explained without having recourse to this 
natural selection theory; and (3) that, therefore, mimicry makes 
natural selection in no wise necessary, and hence lends no basis: 
for its establishing. The author also, in a long discussion of. nearly 
one hundred pages, criticises adversely the selection theories and 
Darwin in general. He holds that the Darwinian theory of species- 
building from varieties is very ill-grounded, but, finds also de 
Vries’s mutations-theory incompetent to explain species, at least, in 
the large degree in which they actually exist. The author presents 
a theory or explanation of his own for species-forming, which is 
essentially this: Variation is not simply a fluctuation about a stable 
mean; it ¢s evolution in small steps. Evolution is the principle of 
life; it is determinate, 2.e., progressive, yet with rapid, slow, or even 
standstill periods. There are differences in the rapidity of evolu- 
tion among similar groups, as classes, orders, families, genera, 
species, races, even individuals, and the two sexes of a kind. This 
accounts for the great variety of life. There is a great variety of 
stages of evolution rather than a great variety of adaptation. 

78 De Vries, Hugo, ‘““The Evidence of Evolution,” Science, N. S., 
Vol. XX, pp. 395-401, 1904. 

*° Lankester, Prof. Ray, Address by, reported in the London Mail, 
September, 1906. 

°° Ammon O., “Der Abanderungsspielraum,’ Naturw. Wochen- 
schr., Vol. XI, pp. 137-143, 149-155, 161-166, 1894. 

*? Bumpus, H. C., “The Variations and Mutations of the Intro- 
duced Sparrow, Passer domesticus,’ in Biological Lectures, Wood’s 
Holl Laboratory, 1897; also, “The Elimination of the Unfit as illus- . 
trated by the Introduced Sparrow, Passer domesticus,’ in Biological 
Lectures, Wood’s Holl Laboratory, 1899; also, “The Variations and 
Mutations of the Introduced Littorina,’ Zool. Bull., Vol. I, pp. 247- 
259, 1808. 


CHAPTER ITV. 


DARWINISM ATTACKED (CONTINUED): THE 
THEORY OF NATURAL SELECTION (CON- 
TINUED). 


CERTAIN objections urged by various authors may be said 
to concern themselves more with the character of the varia- 

Objection based tions themselves and the possibilities of their 
on the linear and 4 ccumulation by selection, than with the manner 
quantitative and ; 
non-qualitative of their occurrence. For example, de Vries’ 
Meine aidan denies the species-forming capacity of Dar- 
tions. Winian selection of Darwinian (fluctuating) 
variation, on the ground that these variations are only 
“linear,” and thus cannot afford a basis for the creation of 
new forms. Already existing bodies, organs, and parts 
can be enlarged or made smaller, made smoother or rougher, 
made bluer or less blue, greener or less green, that is de- 
veloped plus-ward or minus-ward, but by this nothing really 
new is created. But, declares de Vries, the differentiation 
of organs consists, taken by and large, in the development 
of actually new characteristics ; therefore in such material as 
that presented by the linear variations of Darwin, selection 
cannot have the necessary basis for this production of new 
characteristics. 

Gustav Wolff * reiterates the same objection in his declara- 
tion that while the theory of natural selection may get on 
decently well when modifications embodying only quan- 
titative changes in parts or organs are concerned, it is com- 
pletely at a loss to account for modifications or adaptations 
requiring as basis qualitative changes. Even the warmest 


70 


DARWINISM ATTACKED. aE 


advocates of the selection theory have to admit, says Wolff, 
that they face a serious matter here. Weismann ° is quoted 
as follows: “Wenn man sich die Umwandlung deshalb in 
grésseren Schritten und durch Variationen von qualitativer 
Natur geschehend denkt, so wird man uber dieses Hindernis 
nicht wegkommen. Ich glaube aber, dass man von den 
Variationen grdsseren Betrages, wie sie bei domestizierten 
Tieren und Pflanzen nicht selten vorkommen, bei den Pro- 
zessen der Artumwandlung, wie sie in der freien Natur vor 
sich gehen, vollstandig abgesehen hat, dass Mier iiberhaupt 
nicht qualitative sondern nur quantitative Unterschiede der 
Individuen das Material der Naturztichtung bilden, solche 
aber sind immer vorhanden.” Wolff holds that there can 
simply be no doubt that if natural selection can do any 
modifying at all it has at most to limit itself solely to work 
possible on a basis of quantitative variation of already ex- 
isting structures. 

Variation also of whatever kind is subject to Galton’s * law 
of regression. This is, put briefly, that the young of 

Galton'’s law Parents varying from the mean of their species 
of regression Or race tend to vary also in the same direction 
but less so than the parent, so that the mean or mode among 
the young is nearer the species or race type (mean or mode) 
than the parental type was. Or as Morgan” has stated it: 
“The facts of observation show that when a new variety ap- 
pears its descendants are more likely, on the average, to 
produce proportionately more individuals that show the same 
variation, and some even that may go still farther in the 
same direction. If these latter are chosen to be the parents 
of the next generation, then once more the offspring may 
show the same advance; but little by little the advance slows 
down, until before long it may cease altogether. Unless, 
then, a new kind of variation appears, or a new standard of 
variation develops of a different kind, the result of selection 
of fluctuating variations has reached its limit. Our experi- 


72 DARWINISM TO-DAY. 


ence seems, therefore, to teach us that selection of fluctuating 
variations leads us to only a certain point, and then stops in 
this direction. We get no evidence from the facts in favour 
of the view that the process, if carried on for a long time, 
could ever produce such great changes, or the kind of 
changes, as those seen in wild animals and plants.” 

There is something inherent in the make-up of the organ- 
ism and something inevitably incident to the phenomena of 
variation which prohibit, even in the most favourable cases, 
the indefinite movement of variation. Johannsen,’ pro- 
fessor of plant physiology in the University of Copenhagen, 
finds that beans bred in pure lines, 7. e., not crossed, conform 
perfectly with Galton’s law of regression. And Johannsen 
holds that this regression must be a serious brake on the 
species-modifying, 1. e., species-forming, activity of natural 
selection. That is, while the species mode can be moved in 
one direction or another by pure line breeding it can be so 
moved only very slowly. And this same law of regression 
will tend to break up a “mixed population” resulting from 
crossed and miscellaneous breeding into distinct pure lines; 
that is, each independent form-type tends to be constant, not 
constantly moving, 7. e., transforming. New types must 
arise chiefly then through (a) the crossing of races or 
species (= hybridisation) or (b) through mutations. 

Delage ‘ in his criticism of selection makes the point that _ 
because the causes of variation are more feeble than the 

Delage’s eriti- CAUSES of fixity (as evidenced by the massing of 
cism of Delbeuf's variations around and close to the mean or mode, 
oy: and their increasing scarcity as they recede in 
any direction from the mode (species type) ), the species .. 
tends always to stand still rather than to change. If in the 
first generation a thousandth of the individuals vary in the 
same way, in the second generation only 1-1000 of the 
thousandth part will show the same variation, reasons 
Delage. But, as pointed out in chapter vi (“Darwinism De- 


DARWINISM ATTACKED. _ 2 


fended’’), this criticism was long ago met by Delboeuf, who 
claimed to show mathematically that, however feeble may be 
the number of varying individuals compared with those 
non-varying, the number of the varying will always be 
increasing and will finish by being greater than that of the 
individuals holding to the type. Delage holds “Delbceuf’s 
law” to be false as regards its attempted general applica- 
tion to the selection of variation, conceding it to hold true 
only in the hypothetical case where a persistent active modi- 
fying cause influences for some reason but a part of the 
individuals of a species. And Delage cannot conceive of a 
cause endowed with such an attribute. 

An objection that has been often made to the natural 
selection theory may be put in the following general form: 

It may be granted that selection can make evolu- 

Selection may ., : ; : 
produce evolution tion, 7. ¢., adaptive change or progress, but this 
eae not Will be done in such a way as to leave a con- 
species (discon- tinuous chain or series. How is the chain 
Hnuous series) token into species? Areall our species simply 
the existent ends of series or chains? But we see many 
chains or series of discontinuous but obviously connected 
species. Natural selection can make evolution but not 
species. Darwin himself couched this objection more con- 
cisely as follows: “Why, if species have descended from 
other species by fine gradations, do we not everywhere see 
innumerable transitional forms? Why is not all nature in 
confusion, instead of the species being, as we see them, well 
defined ?” 

Professor Morgan, in his “Evolution and Adaptation,” 
discusses this objection in the following paragraphs (pp. 
129-131): 

“The answer that Darwin gives [to his own just quoted 
query| is, that by competition the new form will crowd out 
its own less-improved parent form, and other less-favoured 
forms. But is this a sufficient or satisfactory answer? If 


74 DARWINISM TO-DAY. 


we recall what Darwin has said on the advantage that 
those forms will have in which a great number of new 
variations appear to fit them to the great diversity of 
natural conditions, and if we recall the gradations that exist 
in external conditions, I think we shall find that Darwin’s 
reply fails to give a satisfactory answer to the question. 

“It is well known, and Darwin himself has commented on 
it, that the same species often remains constant under very 
diverse external conditions, both inorganic and organic. 
Hence I think the explanation fails, in so far as it is based 
on the accumulation by selection of small individual varia- 
tions that are supposed to give the individuals some slight 
advantage under each set of external conditions. Darwin’ 
admits that ‘this difficulty for a long time quite confounded 
me. But I think it can be in large part explained.’ The 


\- first explanation that is offered is that areas now continuous 


may not have been so in the past. This may be true in 
places, but the great continents have had continuous areas 
for a long time, and Darwin frankly acknowledges that he 
‘will pass over this way of explaining the difficulty.’ The 
second attempt is based on the supposed narrowness of the 
area, where two species, descended from a common parent, 
overlap. In this region the change is often very abrupt, 
and Darwin adds: 

“ “To those who look at climate and the physical condi- 
tions of life as the all-important elements of distribution, 
these facts ought to cause surprise, as climate and height 
or depth graduate away insensibly. But when we bear in 
mind that almost every species, even in its metropolis, would 
increase immensely in numbers, were it not for other com- 
peting species; that nearly all either prey on or serve as 
prey for others; in short, that each organic being is either 
directly or indirectly related in the most important manner 
to other organic beings,—we see that the range of the in- 
habitants of any country by no means exclusively depends 


DARW ENISMeA TPACKED: 75 


on insensibly changing physical conditions, but in a large 
part on the presence of other species, on which it lives, or 
by which it is destroyed, or with which it comes into com- 
petition; and as these species are already defined objects, 
not blending one into another by insensible gradations, the 
range of any one species, depending as it does on the range 
of others, will tend to be sharply defined.’ 

“Here we have a petitio principu. The sharp definition of 
species, that we started out to account for, is explained by 
the sharp definition of other species! 

“A third part of the explanation is that, owing to the 
relative fewness of individuals at the confines of the range 
during the fluctuations of their enemies, or of their prey, 
or in the nature of the seasons, they would be extremely 
liable to utter extermination. If this were really the case, 
then new species themselves which, on the theory, are at 
first few in numbers ought to be exterminated. On the 
whole, then, it does not appear that Darwin has been very 
successful in his attempt to meet this objection to the 
theory.” 

A rather surprising objection is that of Pfeffer,” who 
contends that selection cannot be the cause of the formation 

of species, for if it were real, however feeble 

Pfeffer's objec- . ; ; 

tion based on the 1tS effects, it would transform species much 
Beas more rapidly than they are transformed; and in 

order to transform a species in a long time the 
protection afforded by the selection of small additions or 
modifications is so feeble as to be illusory. And adequate 
protection under such a system of species transformation 
is imperative. This is a curious argument, for it has always 
been one of the claims of the mutationists that a “hurry- 
up” theory is needed in order to satisfy the familiar objec- 
tion that the physicists’ estimate of the actual age of the 
world is too low to admit of the production of the hosts of 
kinds of animals and plants which we know to have existed 


ay 


76 DARWINISM TO-DAY. 


by the process of natural selection. But Pfeffer, who is 
an ingenious debater, makes out a very plausible case for his. 
contention. 

Of the many special questions that have been asked of the 
selectionists two may be mentioned, simply as examples illus- 
trative of a rather formidable category of objections most 
of which are concerned with certain particular phases of 
evolution or groups of evolution phenomena rather than 
with the whole problem of species-forming. Many such 
special objections or questions touching specific cases were 
taken up and answered by Darwin in his “Origin of 
Species.” Morgan has recently (“Evolution and Adapta- 
tion’) gone over critically many of these special objections: 
and Darwin’s answers to them, and pointed out clearly 
that in numerous cases Darwin relied for his answers on 
evolution factors which the neo-Darwinians have attempted 
to read out of court. In many tight places Darwin availed 
himself of the Lamarckian factor of the cumulation, through 
inheritance, of the effects of use and disuse, or of other 
functional stimuli originating either in internal or ex- 
trinsic conditions. That is, Darwin, while constantly trying 
to rely, and whenever possible relying on natural selection 
as the species-forming and adaptation-explaining cause, 
never hesitated, when it seemed necessary, to admit the 
influence and effect of the inheritance of acquired characters 
or the influence of other, to him, unknown factors. In 
most cases of degeneration, for example, he adopted a 
Lamarckian explanation. 

The question of how sterility between species could have 
arisen is a case in point. ‘That this property of species is 

useful to them in the somewhat unusual sense 
eee Eee that it keeps them from freely mingling with 
species sterility other species is true,’ says Morgan; “but this 
by selection, , : ; 

would be a rather peculiar kind of adaptation. 
If, however, it be claimed that this property is useful to 


DARWINISM ATTACKED. 19% 


species, as Darwin himself claims, then, as he also points out, 
it is a useful acquirement that cannot have arisen through 
natural selection. It is not difficult to show why this must 
be so. If two varieties were to some extent at the start 
less fertile, inter se, than with their own kind, the only way 
in which they could become more infertile through selection 
would be by selecting those individuals in each generation 
that are still more infertile, but the forms of this sort would, 
ex hypothese, become less numerous than the descendants 
of each species itself, which would, therefore, supplant the 
less fertile ones.’”’ Darwin admits that this situation cannot 
apparently be explained by natural selection, and simply 
_ says that to him it appears “that the sterility both of first 
crosses and of hybrids is simply incidental or dependent on 
unknown differences in their reproductive systems.” 

Wolff ° has urged strongly the objection that natural selec- 
tion does not explain the degeneration or atrophy of parts, 

Ou eetiail that at least not large or nearly complete reduction. 
selection cannot And Weismann and other selectionists long 
Beet ae ago conceded that some sort of auxiliary prin- 
generation of ciple was necessary to explain degeneration on 
eee a Darwinian basis. This principle was supplied 
by Weismann, under the name of panmixia, which is, simply, 
that a constantly active selection is necessary not only for 
the evolutionary development or specialisation of an organ 
but as well for its retention in specialised condition.*’ *’ 
So that an organ which is no longer used and is therefore 
useless comes no longer under the supporting influence of 
selection (on the basis of advantage) and must consequently 
degenerate. But, as Wolff says, it seems obvious that such 
an influence or effect of the cessation of selection or of 
panmixia (so-called by Weismann because all variations 
good and bad alike mix and compensate each other) can 
‘at best lead to degeneration or atrophy only when the 
negative or reducing variations are in the majority, for when 


78 DARWINISM TO-DAY. 


this is not the case the average of the survivors cannot 
change. Weismann himself has in recent years recognised 
the inadequacy of panmixia alone to explain degenerative 
phenomena. He says:’* ... “In most retrogressive pro- 
cesses active selection in Darwin’s sense plays no part, 
and advocates of the Lamarckian principle, as above re- 
marked, have rightly denied that active selection, that is, 
the selection of individuals possessing the useless organ in 
its most reduced state, is sufficient to explain the process of 
degeneration. I, for my part, have never assumed this, 
and have on this very account enunciated the principle of 
pannuxia. Now, although this, as I have still no reason 
for doubting, is a perfectly correct principle, which really 
does have an essential and indispensable share in the process 
of retrogression, still it is not alone sufficient for a full ex- 
planation of the phenomena. My opponents, in advancing 
this objection, were right, to the extent indicated, and as 
I expressly acknowledge, although they were unable to 
substitute anything positive in its stead or to render my 
explanation complete. The very fact of the cessation of 
control over the organ is sufficient to explain its degenera- 
tion, that is, its deterioriation, the disharmony of its parts, 
but not the fact which actually and always occurs where an 
organ has become useless—viz., its gradual and unceasing 
diminution continuing for thousands and thousands of years 
and culminating in its final and absolute effacement.” 

To supply the lack in the present neo-Darwinian explana- 
tion of retrogression Weismann calls on his new theory of 
germinal selection, the “rehabilitator of the natural selec- 
tion theory” (for an account of this theory see chapter viii). 
But Wolff and Morgan and others have shown how unsatis- 
factory and inadequate this third attempt at an explanation 
is, even if we grant the actuality of germinal selection, a 
hypothesis which has by no means met with any general 
acceptance by biologists. 


Arg 


DARWINISM ATTACKED. 79 


In all our discussion of the effectiveness of the natural 
selection theory one feature of it has so far not been ques- 
tioned. And that is the actual selecting power when the 
variations or differences among individuals are large enough 
to be conceivably of real advantage or disadvantage to the 
respective organisms. That is to say, we have not brought 
into question the alleged rigour of the struggle for existence 
upon which rigour depends, of course, the selection and the 
survival of the fittest. The very phrases “struggle for ex- 
istence”’ and “‘survival of the fittest” presuppose and assume 
a rigour of competition and a life-and-death-determining 
value of the variations or differences that are fundamental 
features of the natural selection theory. Let us, however, 
not hesitate to scrutinise these basic assumptions of the 
Darwinians. 

What of the actual rigour of the struggle that must be 
presupposed in order to give small variations a life-and- 

Sorutiny of the death-determining worth? Does it exist? Has 
claimed extreme it been observed? Is the actual (admitted) 
sat a the Production of thousands or millions of eggs 
consequent per- or embryos in localities capable of supporting 
sonal selection, pate eee : 

but tens or hundreds of individuals, sufficient 
reason for deducing an endless, searching, utterly rigorous 
competition sufficient to give the slightest variations 
a weight in the balances determining death or life? 
In the first place, this tremendous competition must be 
largely over, if it exists, before the individuals come to 
maturity. Especially is this absolutely true of all species 
that live for a long time in immature stages and a very short 
time in the adult stage, as the Mayflies ** with only a night- 
long adult life. Many insects of complete metamorphosis 
(i. ¢., those whose adult stage, assumed during a quiescent 
encased pupal stage, is very different from their larval 
stage) which have very elaborate structural specialisations in 
the adult stage have had their fate as offspring-producing 


80 DARWINISM TO-DAY. 


agents decided for them in immature, 7. e., egg, larval, or 
pupal, life, and this immature life is in most cases by far 
the larger part of the insect’s duration of existence. 

Henslow ** sowed together the same quantity of two 
kinds of wheat in a square yard of ground. The young 
wheat plants that came up were many times as many as the 
soil could support; the passive struggle for life was intense. 
In the end twenty heads ripened and these were all of one 
of the two kinds sown. The experiment was repeated in 
the following year with the same result. In the struggle 
one kind of wheat had a distinct advantage over the other. 
But this selection depended wholly on special characters or 
strength of the young stages. None of the adult characters 
cut any figure in this selection, which was decided before 
ever the plants came to maturity. And this is true, it seems 
to me, of most of struggle and selection. 

It is not in the adult state that the oppressive abundance 
exists: in the forest to-day are about as many crows as last 
year; in the meadows as many yellow butterflies as in sum- 
mers by. The eggs and the young are the stages which 
figure in mortality tables. They need the variations and 
adaptations ; the pressure is largely gone before maturity is 
reached. However, the adaptations of the fully-developed 
body, in structure and function, certainly do not fall behind 
those of the embryonic and immature stages. Indeed they 
obviously are more complex and perfected. 

But after all what determines just what millions of trout’s 

Indiscriminate C@Zs Shall be destroyed and what thousands 
death, shall hatch small fry? Many a sharp-eyed trout 
fisherman, many a keen-witted nature observer, many a 
trained biologist will answer: Chiefly chance, the luck of 
position, the good fortune of not being devoured by the 
roaming things that paddle or crawl in the upper reaches of 
trout streams. What shall decide when the big whale opens 
his mouth in the midst of a shoal of myriads of tiny 


DARWINISM ATTACKED. 81 


Copepods floating in the pelagic waters of the Aleutian seas, .< 


what Copepods shall disappear forever? Mainly, we may 
say, the chance of position. A bit more or less of size, or 
strength, or redness, or yellowness, or irritability or what 
not of form and function is going to avail little when the 
water rushes into the yawning throat. Now this chance 
and this luck are the luck and chance of the law of prob- 
abilities; that is, luck and chance capable of being mathe- 
matically determined. Given so much ocean, with so many 
whales swimming about in such and such curves at such and 
such rates and opening and closing their mouths inter- 
mittently at such and such intervals, and just so many 
shoals of so many million Copepods, these shoals at such and 
such distances apart, and any mathematical friend will 
reckon for you the chances any one Copepod individual has 
at any given moment of being swallowed. But Darwinian 
variations in the Copepod body will be represented by no 
function in the mathematician’s formula. When the scores 
of little streams dry in California every summer, what deter- 
mines whether millions of Californian water-insects of 
scores of kinds shall die in July or not? Mainly life or 
death is determined for them by their good or ill luck in 
being in one of the few streams that do not dry up, or in 
one of the many that do dry. Kelsey Creek runs into 
Clear Lake, in northern California; it is usually ever-living, 
but some summers it suddenly dries up. Fish play back and 
forth between this stream and the lake; at the time of the 
sudden drying a few hundreds of thousands out of many 
hundreds of thousands that habitually live in the stream and 
adjacent lake waters find themselves one awful day gasping 
painfully for water to wet their drying gills. They gasp a 
short while and then die. Did they all have the same num- 
ber of scales, the same shape and size of body, the same 
tinges of fleeting colour? No, they represented most of the 
possible gamut of Darwinian variation for their particular 


82 DARWINISM TO-DAY. 


species. But they were dead all together, by the ill-chance 
of position. In Lagunita, a small artificial lake on the 
campus of Stanford University, water pours in from two or 
three rivulets during the rainy season so as to fill it and 
make it an abiding place for many aquatic organisms that 
swim in or are washed ih through the dikes. And thou- 
sands of little fishes and water beetles and dragon-fly 
nymphs and the like live contentedly there for seven or eight 
months. But with the rainless summer months come swift 
evaporation and steady leakage, and by September all the 
thousands of little fishes and insects lie dying there together 
in the last few puddles. It is the hard luck of a fatal chance 
against which all the variations in colour, in size, in scales, 
in spines, and what not are as one as far as helping or sav- 
ing any of the gasping possessors is concerned. 

One might go on tiresomely but one does not need to point 
the moral of these tales. Wolff ** has clearly fancied how 
the fate of millions of tapeworms may hang on the recep- 
tion in the German Reichstag of a clever speech for or 
against meat laws. To go so far isn’t necessary: the very 
life-history of the tapeworm and of hundreds of similarly- 
lived vermian parasites shows to what nearly absolute de- 
gree chance rules their fate, and how utterly insignificant 
a part in it miscellaneous individual variation can possibly 
play. 

But aside from the part that what we may call fortune *° 
of position plays in determining life or death among indi- 
viduals, what of the actual rigour of the strug- 
gle in those cases where death does not come 
to thousands at a moment;—in the whale’s 
mouth, by catastrophe of flood or drouth, or by the elephant’s 
tread on the ant-hill? To this question of the rigour of 
intra-specific struggle I have given some personal attention 
in insect life, and while to detail observations here would 
be impossible, I may say baldly that no such rigour of in- 


How real is per- 
sonal selection ? 


DARWINISM ATTACKED. 83 


7 


dividual selection based on variation *’ in colour, in pattern, 
in venation and other wing characters, in hairs and in 
numerous other structural characters, as demanded by the 
needs of the selection theory, is to be detected. I find 
just as much variation represented in series of mature 
individuals collected miscellaneously after having lived for 
more or less time a free life exposed to all the dangers of 
this life, exposed, that is, to the rigour of the individual 
struggle for existence, as among series of similar extent of 
individuals of the same species collected just at the time of 
reaching maturity but before enjoying any opportunity to 
be weeded out (on a basis of disadvantageous variation) 
by the rigour of the life-struggle. Just as many varying 
individuals, with variations of just as much extent and va- 
riety, were found in series exposed to the struggle, in which 
these variations are presumably capable of saving or losing 
life, as among series not yet exposed; in other words, just 
as much variation exists after enduring the selective rigour 
of the struggle as existed on the day when the insects are 
first exposed to it. 

Conn ** expresses his belief concerning destruction by 
chance and the rigour of the struggle as follows: 

Conn’s discus: 42s LiScriminate destruction occurs  con- 
sion of the chances Stantly, and certainly influences the problem of 
crs survival. Of the hundreds of individuals that 
are produced where few can live, many are destroyed in- 
discriminately, independent of the principle of survival of 
the fittest, and of these that are thus killed doubtless some 
are superior to those that survive. This principle of indis- 
criminate elimination does not in the slightest deny the 
force of the principle of survival of the fittest, but only indi- 
cates that its action is not absolutely rigid. The fittest do 
not always survive, for many of them are destroyed. 

“On the other hand the least fit do not always perish. 
Whether an individual shall live or die in the struggle is 


84 DARWINISM TO-DAY. 


largely a matter of accident. Many a well-equipped indi- 
vidual will die, while many another, even though handi- 
capped by decidedly unfavourable characters, will continue 
to live and produce offspring because of some specially 
favourable conditions. Nothing could seem to be more 
decidedly disadvantageous than a broken leg, and, if the 
principle of elimination of the unfit were rigid, broken-legged 
individuals should be speedily destroyed. But it is quite 
common to find animals with broken legs or arms which 
yet succeed in living perfectly well. -They have repaired 
their broken members by processes of bone growth, and have 
been able to carry on their part in the struggle for life and 
survive competition. I have found a frog with the whole 
of both feet bitten off, and yet with the wounds healed, the _ 
animal living without feet, and hence hardly able to swim, (/ 
but side by side in competition with other well-developed 
animals. J have found a clam that in its young condition 
had received a severe rent in one gill, through which, by 
some twist the body had been thrust, giving rise to the 
extraordinary condition of three gills on one side of the 
body and one on the other, a truly monstrous abnormity. 
But this clam had lived to maturity and produced eggs in 
quantities equal to any other clam. 

“Now such instances simply show the complexity of the 
conditions which determine survival. They indicate that 
these animals were favoured in some respects sufficiently to 
counteract the disadvantage of their mutilations. But the 
fact that so many instances are found does show that single 
characters do not always determine survival or elimination. 
The question whether an individual survive is dependent 
upon many factors, of which utility of various organs may 
be one and accident another. What would seem more sure 
from a logical standpoint, than that, in the intense struggle 
for life due to numerous individuals seeking for food, a 
frog who was unable to swim because of the loss of his 


DARWINISM ATTACKED. _ 85 


feet would be sure to be a loser? Even if the inflammation 
caused by the wound did not destroy him, it would seem 
impossible for the animal to obtain his share of food. Of 
course, a footless race would be eliminated in a compara- 
tively short time, but the survival of so many mutilated 
individuals shows that selection is not so rigid as to eliminate 
all unfit individuals, even though their disadvantage be very 
great. 

“Tf a very disadvantageous character may thus fail to pro- 
duce destruction it must be still more true that a favour- 
able character, occurring in a single individual, has really 
little chance for survival. The individual possessing it will 
have to compete with accident, with indiscriminate slaughter, 
and with other conditions which we have just seen may be 
sufficient to preserve even a broken-legged individual. 
Nothing can seem more evident than that the web of the 
foot and the muscles of the legs are of use in swimming, 
and have therefore been developed by the preserving influ- 
ence of natural selection. If anything is of selective value, 
these characters certainly are. But when we find that a 
frog with no feet can survive the struggle for existence, it 
is evidently difficult to believe that single variations, either of 
use or disadvantage, will have any special likelihood of sur- 
viving at the expense of other members of the race, so as 
eventually to replace all others. But only thus can they 
be ‘seized upon by natural selection and preserved.’ ”’ 

There are two important objections to the natural selec- 
tion theory based on the relations of this theory with the 
Wana vO other selection theories, namely sexual 
tion needsthe Selection and artificial selection. Wolff ** has 
pees ey made the criticism that natural selection must 
theory, which is be supported by the sexual selection theory 
eee in order to stand. It makes no pretension of 
explaining those extraordinary secondary sexual characters 
such as ornamentation, songs, dances, odours, etc., which 


86 DARWINISM TO-DAY. 


not only are of no conceivable utility in the struggle for 
existence but are in many cases of obvious disadvantage. 
It relies wholly on sexual selection to explain them, and 
yet in Wolff’s eyes, and indeed in the eyes of most biologists, 
sexual selection is practically discredited. It certainly can- 
not explain some or many of these characters. (See account 
of the sexual selection theory and the criticisms of it in 
the next chapter.) Therefore, say Wolff and other anti- 
Darwinians, natural selection is undermined in just so far 
as it relies on the sexual selection theory to sustain it. 

The other objection is that the natural selection theory 
rests altogether too largely on an unwarranted analogy with 

Natural selec: the phenomena of artificial selection. Plate *° 
tion rests too = -has graphically expressed the contrast between 
largely on an : 
analogy witharti- the facts and processes of the two kinds of 
ficial selection, tection in the following double-column table: 


ARTIFICIAL SELECTION. NATURAL SELECTION. 


(1) rests on the wish (Willen) (1) rests on the wunvolitional 
and intelligence of the breeder, and wunreasoning resultant of 
except in a certain few cases of natural forces. 

“unintentional breeding’ (See 

Darwin, “Origin of Species.”) 


(2) selects exceptional, most (2) is a selection of slight dif- 
widely divergent characters, ferences, appearing simultane- 
which appear only in a few ously in many individuals. 
individuals. 

(3) complete isolation (pure (3) pure breeding is often very 


breeding) of the selected indi- 
viduals. 


(4) often leads to exaggerated 
development and to a sickly dis- 
position, so that the whole con- 
stitution suffers. 

(5) leads comparatively rapidly 
to new forms. 


(6) The = artificially-produced 


difficult through the possibility 
of crossing with the parental 
type. 

(4) effects no injury to the 
whole constitution, but on the 
contrary a strengthening and 
bettering of it. 

(5) The modification of species 
is effected, presumably almost 
always, very slowly, for if it 
were otherwise the appearance 
of new species would be often 
observed. 

(6) The natural races (varie- 


DARWINISM 


races are unstable; they revert 
easily to the ancestral type if 
allowed to run wild; this is so 
probably because of their recent 
origin. 


(7) The = artificially-produced 
taces of the same species are 
in most cases fertile among 
themselves. 


ATTACKED. 87 
ties) are stable; they do not 
revert if the outer conditions 
(environment) remain constant; 
this is so probably because they 
are more firmly established by 
reason of greater age. 

(7) Natural varieties do not 
cross in nature, either with 
each other or with the ancestral 
type. 


The most important contrast between the two kinds of 
selection lies, in my eyes at least, in the results obtained in 
the character of the new forms. As Morgan* well says, 
“we should not lose sight of the fact that even after the most 
rigorous selective process has been brought to bear on 
organisms, namely, by isolation under domestication, we do 
not apparently find ourselves gradually approaching nearer 
and nearer to the formation of new species, but we find, on 
the contrary, that we have produced something quite differ- 
ent. In the light of this truth, the relation between the two 
selective theories may appear quite different from the inter- 
pretation that Darwin gives of it. We may well doubt 
whether nature does select so much better than does man, 
and whether she has ever made new species in this way.” 

De Vries expresses very positively his belief that no artifi- 
cial races are fixed and constant forms, in the sense that 
natural varieties are. And this difference he believes to rest 
on the: radically different method ** of origin of the two 
kinds of forms; the domestic ones through carefully main- 
tained selection; the natural ones through definitive imme- 
diately fixed and enduring mutations. 

If one stops to recall his own familiar knowledge of the 
cultivated plants ** and will roughly classify the cultivated 
fruits and vegetables and ornamental plants with which he is 
acquainted into two categories depending upon the mode of 
reproduction, that is whether by division or by seeds, one 
will be struck by the great preponderance of the first of the 


88 DARWINISM TO-DAY. 


two categories,—the category, namely, of cultivated plant 
races which are reproduced practically exclusively by 
division (1. e., by cuttings, roots, scions, buds, etc.). The 
reason for relying upon this kind of reproduction is, in 
nearly every case, that these races do not breed true to seed, 
1. €., the races are not fixed, are unstable. And even among 
those races which we are accustomed to allow to reproduce 
by seed how necessary it is to maintain the unusual environ- 
ment, the exaggerated excellence of conditions of food 
supply, humidity, protection from natural enemies, etc., if we 
are to be successful in maintaining the parental characters of 
the plant. Let a few individuals escape from the hothouse 
or fertilised and sprinkled garden and see how soon, if they 
can persist at all, they lose their characters of amelioration, 
and become most pitifully unadorned. 

In Pfeffer’s ** eyes the fundamental difference between 
the two selection processes rests on the fact that the breeder 
or plant ameliorator selects his individuals (the “to be 
saved’) on the basis of the character or condition of single 
characteristics, while in nature survival is not determined 
by such conditions, but on a basis of total or all-around fitness 
or advantage. ‘‘The moment,” says Pfeffer, “that one be- 
lieves one’s self to be able to place in parallel, simply and 
directly and in general, the activity of the breeder and the 
activity of the struggle for existence, and from this false 
generalisation deductively to compare the selective work of 
the breeder based on definitive special characters with the 
automatic selective work of nature based on similar specific 
characteristics, that moment one enters the camp of the 
teleologists, whether he is doing it knowingly and will- 
ingly, or not. In short it is a logical fallacy when one as- 
sumes to substitute for the selective action of the breeder a 
mechanically-working natural selection. Only in a single 
kind of case has this position any justification, and this not 
on account of logical correctness but on account of the pecu- 


Namespace 


DARWINISM ATTACKED. 89 


liar identity of the circumstances. And this is when a single 
definitive characteristic is so all-important and dominant in 
the life of a race or species that its presence really has a 
life-and-death-determining value in the struggle for exist- 
ence; in this case the killing out of all the individuals not 
provided with this specific character has the same re- 
sult as an actual selection of the possessors of this char- 
acter. The farther, however, the actual circumstances differ 
from this case, in so far as a number of characteristics, and 
not a single one, determines the outcome of survival, by just 
so much less can the Darwinian explanation be made to 
cover the situation.” - 

De Vries sums up a full and careful discussion ** of 
natural as compared with artificial selection as follows: “In 
conclusion, summing up all our arguments we may state that 
there is a broad analogy between breeding-selection in the 
widest sense of the word, including variety-testing, race- 
improvement, and the trial of the breeding ability on one 
side, and natural selection on the other. This analogy, how- 
ever, points to the importance of the selection between ele- 
mentary species,and the very subordinate rdleof intra-specific 
selection in nature. It strongly supports our view of the 
origin of species by mutation instead of continuous selec- 
tion. Or to put it in the terms chosen lately by Mr. Arthur 
Harris in a friendly criticism of my views: ‘Natural selection 
may explain the survival of the fittest, but it cannot explain 
the arrival of the fittest.’ ” 

Finally I desire to add an objection that has real weight 
with me, whatever may be the personal attitude of other 

Anincreasing naturalists or students to it. And that is, that 
number of work- ; : ; 
ing biologists  @ Constantly increasing number of working 
unsatisfied with biologists find themselves, on a basis of their 
the selection : ae . . 
theories, cumulative individual observation and experi- 
ence and thought, unsatisfied with the explanation of adapta- 
tion and species-forming offered by the selection theories. 


go DARWINISM TO-DAY. 


Men using, or rather, testing, these theories every day in 
their work in field and laboratory, find selection insufficient 
to explain the conditions that their observation and experi- 
ments reveal to them. These men are students in all the 
different lines of biological work; they are zoologists, bota- 
nists, paleontologists; they are students of anatomy, physi- 
ology, cecology, and taxomony (classification); they are 
embryologists, pathologists, animal and plant breeders. 
From all these lines of work come increasing complaints; 
selection cannot explain for me what I see to exist. From 
some the cry is more bitter: selection is a delusion and false 
guide; I reject it utterly. For me, I repeat, this is an 
objection of much significance and importance. Just as 
modern chemistry seems to be finding its long useful atonuic 
theory now a restraint and a hindrance in understanding the 
wonderful new facts that have followed the pushing out of 
investigation into the rich fields of physical chemistry, so 
the biological experimentalists, the students of variation and 
heredity, of life mechanics, of physico-chemical biology, 
are finding the rigid theory of selection’s control of all 
processes and phenomena a rack on which they will no 
longer be bound. 
Coupled with the significance of this general objection to 
the reign of the selection theory—a general objection that 
___ the selectionists will say is simply the objection 
The concessions ; : : : 
ofthe selection- that the selection theory is objected to—is the 
ae added significance of the concessions in the way 
of supporting theories that the neo-Darwinians have made 
to the general increase and sharpness of scientific criticism 
of selection; conspicuous examples are Roux’s theory of the 
battle of the parts, and Weismann’s theory of germinal 
selection. This latter is no less than a neo-Darwinian ex- 
planation of how determinate variation, that is ortho- 
genesis, may be explained non-teleologically. Which is 
practically to rob natural selection of all influence in the 


DARWINISM ATTACKED. gl 


primary determination of lines of descent. But to these 
supporting and concessionary theories we shall come in 
a later chapter. 

To show how definitive and positive an anti-Darwinian 
position is taken by some biologists I shall quote some para- 

Fhe graphs from an interesting short paper by Kor- 
radical anti-se- schinsky,’’ a Russian botanist whose formula- 
lection position, ton of the theory of species-forming by hetero- 
genesis preceded that of de Vries by two years. In this 
paper (which is a vorlaufige Mitteilung published in Ger- 
man preliminary to the issuance, in the publications of the 
Royal Academy of Sciences of St. Petersburg, of a larger, 
more detailed paper) Korschinsky arranges in parallel 
columns the various corresponding or contrasting items of 
the selection theory compared with the heterogenesis theory 
of the author himself (for this full table see chapter xi). 
From this table I quote only the following statements to 
show how differently from the Darwinian view the probable 
effects of the struggle for existence may appear to another 
naturalist and to what radically anti-Darwinian conclusions 
a man may come who interprets the effects of selection in 


26 


this way: 

“The origin of new forms can only occur under condi- 
tions favourable for them, and the more favourable such 
conditions are, that is, the less severe the struggle for ex- 
istence is, the more energetic is their development. Under 
- severe external conditions new forms do not arise, or if they 
appear they are extinguished. 7 

“The struggle for existence, and the selection annie goes 
hand in hand with it, compose a factor which restricts new- 
appearing forms and restrains wider variations, and which is 
in no way favourable to the production of new forms. It 
is indeed an inimical factor in evolution. 

“Were there no struggle for existence, then there would 
be no extinguishing of arising or already arisen forms. The 


g2 DARWINISM TO-DAY. 


organic world could then develop into a mighty tree, whose 
branches could all remain in blooming condition, so that 
the now isolated extremest species would be united with all 
others through gradatory forms. 

“The adaptation resulting from the effects of the struggle 
for existence is absolutely not identical with advance, for 
higher-standing, more complex forms are by no means 
‘always better adapted to outer conditions than the lower 
ones. The evolution [used here by the author as synony- 
mous with advance or progressive complexity] of organisms 
cannot be explained in a purely mechanical way. In order 
to explain the origin of higher forms from lower it is neces- 
sary to postulate in the organisms a special tendency to ad- 
vance which is nearly related to or identical with the 
tendency to vary, which tendency compels the organisms 
to advance so far as the outer conditions permit.” 

These declarations sound strange and perhaps almost 
absurd in the ears of one accustomed for years to 
hear only the Darwinian interpretation of the effects of the 
struggle for existence and natural selection. But taken 
up one by one, as they are by Korschinsky, and developed 
and explained, they begin to have a kind of plausibility, 
an appeal to our reason, of much that sort which the Dar- 
winian interpretation has and makes. After all the Darwin- 
ian interpretation is proved only in so far as it possesses a 
high degree of plausibility and makes a convincing appeal 
to our reason. Of exact proof, in the nature of observed 
fact or result of experiment, or of mathematical demonstra- 
tion, there is little in the case either of the Darwinian or 
the Korschinskian interpretation. 

Those other biologists ** who, like Korschinsky, take the 
extreme and positive stand that the struggle and selection 
are not factors in evolution, or if factors are really hinder- 
ing and opposing ones, constitute, however, by far the 
smaller body in the ranks of the anti-Darwinian critics when 


DARWINISM ATTACKED. 93 


compared with those whose arraignment of selection is 
chiefly a protest against its assumption of altogether an 
undue share of influence in species-forming, and whose 
principal attempt is to reduce selection to a secondary place 
among evolutionary factors, giving first place to that influ- 
ence or those influences which determine the character and 
direction of variation. Still the totally anti-Darwinian 
critics are not few, and are not without ingenuity and 
capacity in debate. 

But better justified by what we know to-day and far saner 
in their estimate of the Darwinian factors are such critics 
as Delage and Morgan. “The conclusion of 
this criticism,” says Delage,” at the end of a 
detailed critical discussion of the “true role of 
selection,’ “is that selection is powerless to form species. / / 
Its role, however, is not nul, but it is limited to the sup-} : 
pression of variations radically bad, and to the maintaining | 
of the species in its normal character. Far from being an | 
instrument for the evolution of species it guarantees their’ 
fixity.” And elsewhere he says: “Species come from fixed 
variations. The formation of species is due ordinarily to 
general variation [a conception of change much like that of 
de Vries’s mutations and sudden fixed origin of elementary 
species], very rarely to strong individual variation [sports or 
discontinuous variations], and never to weak individual 
variation [fluctuating or Darwinian variation]. 

Morgan in a recent popular essay in which he takes a 
strong stand against natural selection as a species-forming 

oraviena: factor and in favour of “definite variations” 
verse criticism of (de Vriesian mutations) concludes as follows: 
toasty “In the preceding pages I have tried to bring 
lection. into contrast the point of view of the 
Darwinian school and the newer conception of the sur- 
vival of elementary species. I have tried to show what 
selection has meant to the selectionists. They have 


Delage’s esti- 
mate of selection. 


04 DARWINISM TO-DAY. 


never hesitated to take each particular character of an 
animal or plant, and dress it up in more perfect gar- 
ments, while the body of the species, if I may so speak, 
has been left as it was before. There has been a con- 
tinual tampering with the characters of the organism with 
the laudable intention of doing with them that which na- 
ture herself seems unable to do, namely, to dissociate them 
from the rest of the organisation and perfect them in this 
way or in that. It is this meddling with the fluctuating 
characters of the species that has been the characteristic 
procedure of the Darwinians, in their attempt to show how 
new species have been created. In contrast to this method, 
the theory of the survival of species assumes that a form 
once made does not have its individual parts later disso- 
ciated and adjusted to better fit the external needs of the 
species. Such a new form can change only by becoming 
again a new species with a new combination of characters ; 
some of which may be more developed in one direction than 
before, others less, etc. 

“New forms on the Darwinian theory are supposed to be 
created by a process of picking out of individual differences. 
If, in addition to this, Darwin supposed that at times varie- 
ties and species crowd each other out nothing new is thereby 
_created.* On the other hand the theory of the survival of 
| definite variations refers the creation of new forms to an- 

*“Tf the survival of certain species determines, in a metaphorical 
sense, the kinds of future mutations that occur, the course of evo- 
lution may appear to be guided by selection or survival; but, how- 
ever true it may be that selection acts by lopping off certain 
branches, and limits to this extent the kinds of possible future muta- 
tions, the origin of the new forms remains still a different question 
from the question of the survival of certain species. This negative 
action of selection is not the process that most Darwinians have 
had in mind as the source of the origin of new species. It is true 
that Weismann believes that selection of individual differences deter- 
mines the origin of new species, and that the creation of these new 


species determines the future course of variations in the same direc- 
tion, but his argument that fluctuating variations can go on indefi- 


DARWINISM ATTACKED. _ 95 


other process, namely, to a sudden change in the character } | 


of the germ. The creating has already taken place before 
the question of the survival of the new form comes up. 


After the new form has appeared the question of its per-| 


sistence will depend on whether it can get a foothold. The 
result is now the same as when species crowd each other 
out. This distinction appears to me to be not a matter of 
secondary interest, but one of fundamental importance, for 
it involves the whole question of the ‘origin of species.’ So 


far as a phrase may sum up the difference, it appears that | 
new species are born; they are not made by Darwinian — 


methods, and the theory of natural selection has nothing to 


do with the origin of species, but with the survival of already | 


formed species. Not selection of the fittest individuals, but 
the survival of the sufficiently fit species. 

“There is a fundamental difference between the idea that 
fluctuating variations become specific characters through 
accumulation by selection, and the idea that new species 
arise as definite variations, which, with their appearance, 
characterise the new form as a new species. According 
to the Darwinian theory, natural selection performs a double 
duty, first, to build up new species, and second, to maintain 
them in competition with other species. According to the 
other view, species are not formed by any kind of selection, 
and the question of survival only concerns the maintenance 
of species already formed. The primary problem is the 


problem of the ‘origin of species.’ The central idea is not , 


nitely varying in the direction of selection is refuted by what has 
been actually found to be the case when the process of selection of 
fluctuating variations is carried out. Most of the individuals of a 
species may be brought in this way to show the particular character 
selected in its highest degree as a fluctuating variation, but it appears 
not possible to transgress this limit; and rigorous selection in every 
generation is necessary to hold the individuals to the highest point 
reached. Only by the appearance of new definite variations can a 
given character be permanently fixed, or a new species created that 
will show fluctuating variations around the new standard. 


96 DARWINISM TO-DAY. 


what species survive, but how species originate; no matter 
whether they are going to become victorious or not. 

“After a species has appeared it will surely be admitted by 
every one, that forms that can survive will survive! If 
Darwin’s theory meant only this to those who adopted it, 
is it not surprising that such a truism should have been 
hailed as a great discovery? Was not the theory heralded 
because it seemed to explain how new species arose? What 
shall we say then when we find a situation like that existing 
at the present time, when we are told that after all the only 
difference between Darwin’s theory of natural selection and 
the theory of the survival of definite variations is that in the 
one case fluctuating variations are selected, and in the other 
mutations, and that in both cases natural selection is the 
key to the evolutionary process! Is not the ‘origin of 
species’ still the real point at issue? 

“T yield to no one in admiration for what Darwin has done 
in behalf of the biological sciences, for he succeeded, where 
the great French zoologists failed, in establishing the prin- 
ciple of evolution. Furthermore no other hypothesis, that 
has as yet been proposed, accounts so well for the wide- 
spread occurrence of adaptation of organisms to the environ- 
ment as does the principle of natural selection. But appre- 
ciation of Darwin’s claims in these directions need not blind 
us to the insufficiency of the theory of natural selection to 
account for the origin of species; nor to the fact that his 
followers have been especially concerned in propounding 
and making application of this side of the theory. They 


/have shown little interest in selection as the great conserv- 


‘ing factor of evolution, and the reason for this is not far 
_ to seek, because of the much greater importance that they 
have attributed to natural selection as a creative factor in 


) building up individual differences into specific characters.” 


DARWINISM ATTACKED. 97 


APPENDIX. 


De Vries, H., “Die Mutationstheorie,’ Vol. I, pp. 83 ff., I9goI. 

2 Wolff, Gustav, “Der gegenwartige Stand des Darwinismus,” p. 
9, 1806. 

* Weismann, A., ‘“Aufsatze itber Vererbung,” p. 116, 1892. 

* Galton, Francis, ‘‘Natural Inheritance.” I quote from Galton as 
follows: 

“As soon as the character of the problem of filial descent had 
become well understood, it was seen that a general equation of 

Calton’s state- the same form as that by which it was expressed, 
mentofthelaw also expressed the connection between kinsmen in 
of regression. = every degree. The unexpected law of universal re- 
gression became a theoretical necessity, and on appealing to facts, 
its existence was found to be conspicuous. If the word “peculiarity” 
be used to signify the difference between the amount of any faculty 
possessed by a man and the average of that possessed by the popu- 
lation at large, then the law of regression may be described as 
follows: Every peculiarity in a man is shared by his kinsmen, but 
on the average in a less degree. It is reduced to a definite fraction 
of its amount quite independently of what its amount might be. 
The fraction differs in different orders of kin, becoming smaller 
as they are more remote. When the kinship is so distant that 
its effects are not worth taking into account, the peculiarity of the 
man, however remarkable it may have been, is reduced to zero in 
his kinsmen. This apparent paradox is fundamentally due to the 
greater frequency of mediocre deviations than of extreme ones, 
occurring between limits separated by equal widths’ (pp. 194-195). 

“The law of regression in respect to stature may be phrased 
as follows: namely, that the deviation of the sons from P are on 
the average equal to one-third of the deviation of parent from P, 
and in the same direction or more briefly still; if P + (4D) be 
the stature of a parent, the stature of the offspring will on the 
average be P + (+1-3 D)” (p. 104). 

“Thus, however paradoxical it may appear at first sight, it is 
theoretically a necessary fact, and one that is clearly confirmed 
by observation, that the stature of the adult offspring must, on the 
whole, be more mediocre than the stature of their parents; that is 
to say, more near to the M of the general population” (p. 95). 

“The law of regression tells heavily against the full hereditary 
transmission of any gift. Only a few of many children would 
be likely to differ from mediocrity so widely as their mid-parent, 
and still fewer would differ as widely as the more exceptional of 


98 DARWINISM TO-DAY. 


the two parents. The more bountifully the parent is gifted by 
Nature, the more rare will be his good fortune if he begets a son 
who is as richly endowed as himself, and still more so if he has 
a son who is endowed yet more largely” (p. 106). 

*> Morgan, T. H., ‘““Evolution and Adaptation,” p. 104, 1903. 

* Johannsen, W., “Uber Erblichkeit in Populationen und in reinen 
Linien,” 1903. 

7 Delage, Yves, “L’Hérédité,” 2d ed., p. 398, 1903. 

® Pfeffer, G., “Die Umwandlung der Arten,”’ p. 26, 1894. 

° Wolff, G., ““Beitrage zur Kritik der Darwin’schen Lehre,” pp. 50 
ff. I quote as follows: 

“Fir jeden, der sich den Grundgedanken der Selektionstheorie 
auch nur einigermassen klar gemacht hat, kann kein Zweifel dart- 
Wolf's criticism ber bestehen, dass die nattirliche Selektion immer 
of panmixia. nur ein einziges Anpassungsgebilde, niemals aber 
zwei oder gar noch mehr zu gleicher Zeit ziichten kann. Es konnen 
z. B. Auge und Ohr nicht gleichzeitig geztichtet werden, denn sonst 
miissten ja die ausgelesenen Individuen mit den besten Augen 
zugleich auch diejenigen mit den besten Ohren sein, eine Vorausset- 
zung, die wir um so weniger machen durfen, als dieselbe ja auf 
alle ubrigen Organe ausgedehnt werden musste. Die Naturzuchtung 
wird sich immer auf die Zuchtung desjenigen Organes verlegen, 
dessen bessere Ausbildung fur das Tier den grosseren Vorteil 
bietet." Ist ein gutes Auge nitzlicher, als ein gutes Ohr, so 
sind die Individuen mit den besten Augen denen mit den besten 
Ohren gegentiber in Vorteil: sie werden geztichtet. Wahrend also 
das Auge gezuchtet wird, steht das Ohr nicht unter dem Einfluss 
der Selektion, also unter dem Einfluss der Panmixie. Unter diesem 
Einflusse stehen aber sdmtliche Organe mit Ausnahme des ein- 
zigen, welches gerade geziichtet wird, sie fangen daher alle an, 
einen Ruckbildungsprozess einzugehen. Sobald nun eines der nicht 
gezuchteten Organe bereits so weit riickgebildet ist, dass der Zu- 
stand desselben eine Gefahr fiir den Organismus in sich schliesst, 
alsdann wird sich die Naturztichtung diesem Organe zuwenden, 
denn dann ist eine bessere Ausbildung dieses Organes ein grosserer 
Vorteil als die des andern. Die Selektion iiberlasst also dieses 
letztere seinem Schicksal, d. h. der riickbildenden Panmixie, unter 
deren Einflusse die andern Organe immer noch stehen. 


*Jedes Gebilde, welches durch Naturztichtung hervorgebracht ist, 
auch wenn es jetzt von untergeordneter Bedeutung ist, muss einmal 
Generationen hindurch, d. h. so lange als die Selektion zu seiner 
Herstellung brauchte, das allerwichtigste gewesen sein, eine Konse- 
oe die allein gentgt, den ganzen Darwinismus ad absurdum zu 
thren. 


DARWINISM ATTACKED. 99 


“Wem die Absurditat dieser ganz unvermeidlichen Konsequenzen 
noch nicht einleuchtet, der moge sich die Sache an einem Bilde 
versinnlichen. Wenn ein Lehrer eine Klasse von Schilern zu 
unterrichten hat und dabei so verfahrt, dass er immer einen Schuler 
zu sich auf sein Zimmer nimmt und dort unterrichtet, unterdessen 
aber die ubrigen treiben lasst, was sie wollen, so wird er bei einer 
Inspizierung durch den Schulrat mit seiner Klasse wenig Staat 
machen konnen, weil die Schtiler weit mehr Zeit auf das Vergessen, 
als auf das Behalten und Lernen verwendet haben. Sie werden 
daher nicht nur das, was sie bei diesem Lehrer in den wenigen 
Einzellektionen, sondern auch das, was sie in den frithern Klassen 
gelernt hatten, vergessen haben. Genau so beim Organismus. Alle 
Organe stehen eine weit langere Zeit unter dem Einflusse der Pan- 
mixie, als unter dem der Selektion; wenn also die Panmixie einen 
Einfluss austbt, so wird dieser Einfluss der tberwiegende sein, und 
wenn dieser Einfluss dem der Selektion entgegengesetzt ist, so wird 
der Einfluss der Selektion ganzlich aufgehoben werden, d. h. der 
rickbildende Einfluss wurde die Oberhand behalten, das ganze 
Tier mtisste sich mit Stumpf und Stiel—zurtckbilden, ein Vorgang, 
bei welchem die Panmixie zu vergleichen ware einem Feuer, das 
ein Dorf ergriffen hat, die Selektion dagegen einer Feuerwehr, 
welche mit der Spritze immer wieder an dasjenige Haus fahrt, aus 
dem gerade die starksten Flammen herausschlagen. Diese Feuer- 
wehr wird gewiss nicht viel von dem Dorfe retten. 

“Der Darwinismus muss also, wenn er der Absurditat dieser 
Konsequenzen entgehen will, notwendig annehmen, dass diejenigen 
Organe, welche jeweilig nicht unter dem Einflusse der Selek- 
tion stehen, ruhig und unbeschadet warten konnen, bis die mutter- 
liche Sorgfalt der Selektion, welche sich immer nur einem ihrer 
Kinder widmen kann, sich ihrer wieder annimmt. Das heisst der 
Darwinismus muss annehmen, dass die Panmixie keinen Einfluss 
auf die Organisation hat. 

“Da aber die Variierung eine Thatsache ist, so muss er anneh- 
men, dass gtinstige und ungiinstige Variierung die gleiche * Wahr- 
scheinlichkeit haben, womit ein weiterer Beweis geliefert ist, dass 
der Darwinismus nur mit graduellen Veranderungen rechnen kann. 

“Die Lehre von der Panmixie und die Selektionstheorie vertragen 
sich nicht mit einander. Aus der Richtigkeit der einen folgt die 
Falschheit der andern. Und insofern die Selektionstheorie eigentlich 
die Voraussetzung zur Lehre von der Panmixie ist, vernichtet diese 
letztere sich selbst durch ihre blosse Existenz. Ihre Bejahung 

*Ist man, wie Emery, der Ansicht, dass ungiinstige Variierungen 


grossere Wahrscheinlichkeit haben_ als giinstige, so muss man 
hieraus allein die Unrichtigkeit der Selektionstheorie folgern. 


100 DARWINISM TO-DAY. 


schliesst ihre Verneinung in sich, d. h. sie leidet an einem unlosbaren 
inneren Widerspruch.” 

1° This necessity of constantly active selection must apply as well 
to specialised function as to specialised organ. But it is not diffi- 
Example of inef- cult to call attention to certain functions or physio- 
fective panmixia. logical capacities of various animals which seem to 
negative this declaration of the need of constant selection to main- 
tain specialisation. For example, I have shown (‘Regeneration in 
Larval Legs of Silkworms,” Jour. Exper. Zool., Vol. I, pp. 593-599, 
10 figs., 1904) that the long ‘‘domesticated” mulberry silkworm larva 
possesses the capacity of regenerating any of its legs, if the mutila- 
tion has not removed the whole appendage. Now the assumption 
of most selectionists is that this capacity for regenerating injured 
legs and other parts is a specialisation, adaptive and advantageous. 
But in connection with this particular case, it should be borne in 
mind that the silkworm has been for approximately 5,000 years a 
domesticated animal, cared for under such conditions as to make 
the natural loss of legs almost an impossible occurrence. Perfectly 
protected against such natural enemies as bite off legs, there has 
certainly been nothing of that sharp necessity, during all the life of 
countless generations of silkworms, which is supposed to be the 
basis for maintaining the advantageous capacity for regeneration. 
There has been a clear field for panmixia. But the regenerative 
capacity still exists in effective degree. 

11 See a recent paper by Vejdovsky (“Uber einige Siisswasser- 
Amphipoden, III, Die Augenredtiktion bei einem neuen Gam- 

Example of pro- mariden aus Irland und uber Niphargus caspary 
gressive degener- Pratz aus den Brunnen von Miinchen,” in S. B. Kgl. 
ation not expli- . we 
cable by natural Bohm. Ges. d. Wiss., 1905), embodying the results of 
selection, his studies on the reduction of the size in certain 
small Crustaceans (Gammaridz), which he found living in the Irish 
Sea at a depth of from 130 to 150 feet. These Crustaceans form 
an interesting series showing a gradual reduction of the eyes. It is 
shown clearly that this reduction proceeds very regularly from the 
periphery toward the interior. First, there is apparent a high degree 
of variability of all parts, then the optic parts of the eye disappear, 
and finally the nervous, or retinal, parts. This course of reduction 
is only explicable, according to the author, on a basis of the 
inherited degenerative results of a lack of use, for in any decreas- 
ing use exactly this course of individual degeneration of the eye 
is what is met with; that is, the active external optic elements 
degenerate first, and later the nervous, or retinal, elements. 

** Weismann, A., “On Germinal Selection as a Source of Definite 
Variation,” trans. McCormack, pp. 38 ff., 1896. 


DARWINISM ATTACKED. IOt 


*® The Mayflies, or lake-flies, constitute an order (Ephemerida) 
of insects which spend from several months to perhaps a couple 
of years in their immature life (as crawling, gill-bearing, wingless. 
aquatic larve), and from a few hours to at most a few days as. 
free-flying adult creatures. Many other insects (indeed most in- 
sects) have a much shorter adult life than immature life, and 
most of them have very different structures in the two life-periods. 
Hundreds of insect kinds take no food in the adult stage and many 
others that do have food-habits quite different from the larval habits.. 

** Henslow, G. W., “Origin of Flowering Structures,” 1895. 

*® Wolff, G., “Beitrage zur Kritik der Darwin’schen Lehre,” pp. 41,. 
ff., 1898. I quote as follows: 

“Ware die Wahrscheinlichkeit einer ntitzlichen Variierung wirk- 
lich so klein, wie Emery behauptet, ware sie wirklich so klein, wie 

Wolff's discus- die Wahrscheinlichkeit, dass in dem Satz einer 
sion of the selec- Druckseite durch beliebiges Ersetzen eines beliebigen. 
tion coefficient. Biuchstaben durch einen beliebigen andern ein Druck- 
fehler verbessert wird, dann konnte sich der Darwinismus gleich 
von vornherein begraben lassen. Er konnte dann nicht mehr sagen: 
die Auslese des Bessern muss notwendig eine Steigerung des. 
Niutzlichen ergeben. Die erforderlichen Voraussetzungen waren dann 
noch viel verwickelter; es miisste dann auch noch tiber den Inten- 
sitatsgrad * des Selektionsprozesses eine Voraussetzung gemacht 
werden: er muss so hoch sein, dass die Summe aller tberlebenden 
+ dx’ (unter denen vor Eintritt des Selektionsprozesses die unge- 
heure Mehrzahl negativ, das Vorhandensein positiver dageger 
ausserst unwahrscheinlich war) eine positive Zahl wird. Der 
Kampf ums Dasein an und fiir sich ntitzt also noch gar nichts; 
erst wenn er jenen ganz bestimmten Intensitatsgrad erreicht, dann 
erst wirkt die Selektion verbessernd. Und wie hoch ist dieser von 

* Dieser Intensitatsgrad ist eine genau bestimmte, wenn auch 
selten bestimmbare Zahl. Sie giebt das Verhaltnis der erzeugten zu 
den sich fortpflanzenden Nachkommen an. Man konnte diese 
Verhaltniszahl den Selektionskoeffizienten nennen. 

* Ich muss trotz der Einwendungen Emerys meine Schreibweise 
dx beibehalten. Sage ich, dass der Darwinismus mit dem Vari- 
ierungsinkrement nur dann rechnen durfe, wenn er von ihm keine 
bestimmte Grosse voraussetzt, sondern ihm gestattet, sich der Null 
beliebig zu nahern, und will ich dies durch ein mathematisches 
Zeichen ausdriicken, so ist das einzig richtige dx. Ob die wirk- 
lichen Variierungsinkremente messbar sind oder nicht, ist dabei 
ganz gleichgiltig. Ubrigens ist Emery im Irrtum, wenn er meint, 
alle seien messbar. Die wenigsten sind es. Die Differenz in der 
Disposition zur Tuberkulose zwischen zwei vollig gesunden Indi- 
viduen ist z. B. gewiss nicht messbar, und doch kann gerade hier 
eine, wenn auch noch so kleine Differenz, im Kampf ums Dasein 
den Ausschlag geben. 


102 DARWINISM TO-DAY. 


Emery geforderte Intensitatsgrad! Nimmt man an, ein Tier habe 
40,000 Millionen Kinder, von welchen nur 2 Individuen sich fort- 
pilanzen, so ware nach Emerys Rechnung dieser Selektionsprozess 
noch nicht einmal intensiv genug, um es wahrscheinlich werden zu 
lassen, dass diese 2 im Durchschnitt sich irgendwie verbessert 
haben.* Und dabei ist noch vorausgesetzt, dass die Selektion von 
den 40,000 Millionen wirklich ganz genau die 2 Besten heraus- 
gefunden hat. Dies wird nattrlich nie der Fall sein. Denn je 
geringer die Prozentzahl der gtinstigen Variierungen ist, um so 
weniger wird das Resultat der Selektion von Variierungsvorteilen, 
um so mehr dagegen von Situationsvorteilen abhangen. Nehmen 
wir z. B. eine Tierklasse, bei welcher die Verhaltniszahl der erzeug- 
ten und der erhaltungsfahigen Individuen der von Emery geforderten 
Zahl vielleicht am nachsten kommt: die Bandwiirmer. Nehmen 
wir also an, ein Bandwurm erzeuge wahrend seines ganzen Lebens 
40,000 Millionen Eier. Unter den abgehenden Eiern findet eine 
Selektion statt: nur die, welche vom Zwischenwirt gefressen werden 
konnen sich zur Finne entwickeln. Es werden aber ungeheuer 
wenige gefressen, die meisten gehen ungefressen zu Grunde. Wir 
haben also eine intensive Selektion. Wovon hangt es aber ab, ob 
das Ei gefressen wird? Ganz ausschliesslich von aussern Umstan- 
den. Die individueilen Eigenschaften der Eier kommen nicht in 
Betracht. Wir haben also hier einen Selektionsprozess, bei 
welchem ein Einfluss der Variierungsvorteile absolut ausge- 
schaltet ist, bei welchem ausschliesslich Situationsvorteile in Be- 
tracht kommen. Nur in Bezug auf die Resistenzfahigkeit konnten 
Variierungsvorteile von Belang sein, die wir aber ausschalten 
konnen, indem wir uns auf ein bestimmtes Anpassungsgebilde 
beschranken (was tiberhaupt bei jeder Darwinistischen Betrachtung 
notig ist), z. B. die Entstehung der Saugnapfe, etc. Dass unter 
den relativ wenigen gefressenen Eiern sich eines von den 2 mit 
einer in Bezug auf die Saugnapfe vorteilhaften Keimesanlage 
befinde, ist ausserst unwahrscheinlich. Die gefressenen Embryonen 
kommen nun ‘zur engeren Wahl.’ Nicht alle werden in fremden 
Organismus bleiben. Viele werden einfach abgehen. Bei diesem 
Selektionsprozess, der lange nicht so intensiv ist, als der erste, 


1 Wobei noch zu beachten ist, dass die Zahl 100 der Elemente, in 
welche Emery ein Organ sich aufgelost denkt, selbstverstandlich 
eine willkirliche ist, und dass diese Zahl der Wirklichkeit nattirlich 
um so naher kommen wird, je grOsser sie angenommen wird. Wie 
enorm wtirde sich dann erst die Zahl der Kombinationen vermehren! 
Ubrigens kommt es auf die Zahlen gar nicht an: das Wichtige ist, 
dass mit der Emeryschen Annahme der Hypothesenkomplex, 
welchen die Selektionstheorie darstellt, um eine neue und zwar das 
Fundament betreffende Hypothese vermehrt wurde. 


DARWINISM ATTACKED. 103 


konnen auch (aber keineswegs ausschliesslich) Variierungsvorteile 
mitwirken. Die soweit gelangten Finnen kommen nun zu einer 
noch engern Wahl. Nur diejenigen entwickeln sich weiter, deren 
Zwischenwirte gefressen oder gegessen werden. Diesen Selektions- 
prozess kOénnen wieder eine Unzahl der verschiedensten Faktoren 
beeinflussen. Mehr oder weniger grosser Geschmack an rohem 
Fleisch, mehr oder weniger grosse Achtsamkeit der Sanitatsbehor- 
den, diplomatischer Notenwechsel tber Grenzverkehr: das sind alles 
Faktoren, die in Betracht kommen konnen. Eine schneidige Reichs- 
tagsrede kann unter Umstanden tuber Tod und Leben von Tau- 
senden von Bandwiirmern entscheiden. Eine Klasse von Faktoren 
kommt aber ganz gewiss nicht in Betracht, das sind individuelle 
Vorteile der Finnen. Auch hier ist also die Wirkung der Vari- 
ierungsvorteile ausgeschaltet. Unter den gefressenen oder geges- 
senen Finnen findet wahrscheinlich wiederum ein Selektionsprozess 
statt, bei welchem Variierungsvorteile (aber keineswegs ausschliess- 
lich) mitwirken konnen. Von den 2 Individuen mit vorteilhaft 
variierten Saugnapfen wird aber aller Wahrscheinlichkeit nach kein 
einziges zur letzten Wahl gekommen sein. Also selbst bei denjeni- 
gen Tieren, bei welchen die Uberproduktion die grésste ist, kénnte 
nach der Emeryschen Rechnung die Selektionstheorie zur Erkla- 
rung der Anpassungserscheinungen nicht mehr verwendet werden.” 

*® See Piepers, M. C., ““Mimikry, Selektion, Darwinismus,” 1903, 
pp. 376 ff. Author shows how an enormous mortality among 
oysters can occur without any reference to their fitness for lite, 
and also gives other interesting cases of indiscriminate non- 
selective mortality. 

7 Kellogg and Bell, “Studies of Variation in Insects,’ Proc. 
Wash Acad. Sci., Vol. VI, pp. 203-332, 1904. I quote the follow- 
ing: 

“There are certainly few selectionists left who honestly believe 
that the minute fluctuating variations in pattern, in size, in curve 

Example of non- of a vein, in length of a hair, etc., have that life- 
selection of trivial and-death value which is the sole sort of value that 
differences. an ‘advantageous variation’ must have to be a ser- 
viceable handle for the action of natural selection. As a matter 
of fact, no systematist will have escaped having had it distinctly 
impressed on him that he recognises differences in the pattern of 
lady-bird beetles, in the number of fin rays in fishes, in the branch- 
ing of a vein in flies’ wings, that no enemy, no agent of natural 
selection, can recognise, at least to the extent of pronouncing 
sentence of death (or not pronouncing it) on its basis. And 
further, no biologist really satisfies himself with the worn state- 
ment, ‘We must not presume to judge the value of these trivial, 


104 DARWINISM TO-DAY. 


these microscopic differences, for we do not know all the complex 
interrelation and interaction of the organism and its environment.’ 
We do not, but we do know for many cases that such differences 
are actually not of life-and-death selective value, and reason 
compels us to believe to a moral certainty that in other cases these 
fortuitous trivialities have similar lack of life-and-death importance. 
The case of the variation of the convergent lady-bird beetle, Hip- 
podamia convergens (p. 275 et seq.), is distinctly in point. In our 
account of this variation we have called attention to the suggestive- 
ness, in its light on the rigour of the ‘struggle for existence’ among 
individuals, of the fact that among several thousand individuals, 
gathered together to hibernate after an active life, having been 
exposed to the attacks of bird and insect enemies, to the rigours 
of climatic conditions and to the necessities of obtaining food 
(other smaller insects, as aphids, etc., caught alive), such a range 
of variation in pattern is found as enables us to describe (so that 
they may be actually readily distinguished by verbal description), 
eighty-four ‘aberrations’ or pattern-variates; lady-birds with no 
spots, with one, with two, with three, with each of all the numbers 
up to and including eighteen distinct small black spots, the different 
numbers usually being represented by several different combinations 
of spots. Systematic entomologists describe Hippodamia convergens 
as a brown-red beetle with six black spots on each elytron, and this 
description is true for most beetles of this species. But not at all 
for all; nor even approximately for many. After a season of ex- 
posure to the struggle for existence, to the rigours of selection, 
individuals with one spot, with six spots, with twelve spots, with 
eighteen, find themselves alive and healthy; they come together 
to pass a quiet winter under the fallen oak leaves on a mountain 
side, ready to mate miscellaneously in the spring, and produce young 
of all manner of pattern (as far as number and arrangement of 
spots go); which young, whether twelve-spotted as they ought to 
be, or no-spotted, or eighteen-spotted as they may be, will appa- 
rently go safely through life despite the malevolent search of the 
all-powerful Inquisitor, Rigour of Selection! 

“Directly touching this point, too, are our data of the variation 
of series of honey-bees collected from free-flying individuals after 
exposure as adults to the rigours of outdoor life, as compared with 
the variation in the series of bees, adult, but collected just as issu- 
ing from the cells before being exposed as adults in any way to 
the external dangers of living. Series of both drones and workers 
representing both exposed and unexposed individuals were studied. 
The results of this examination are, put in one statement, that the 
variation among the exposed individuals is no less than that among 


DARWINISM ATTACKED. 105 


the unexposed individuals. This means that these various, mostly 
slight, blastogenic variations (although in such important organs 
as the wings) which occur among bees at the time of their issuance 
as active, winged creatures, are not of sufficient advantage or dis- 
advantage to the individuals to lead to a weeding out (by death) 
or saving of such varying individuals by immediate selective action. 
Whatever the rigour and danger of the outdoor bee life, these 
variations seem to be insufficient to cut any figure in the persist- 
ence or non-persistence of any individual in the face of this rigour.” 

*® Conn, H. W., “The Method of Evolution,” pp. 72 ff., 1900. 

*° Wolff, G., “Beitrage zur Kritik der Darwin’schen Lehre,” pp. 
24 et seq., 1808. 

2° Plate, L., “Uber die Bedeutung des Darwin’schen Selections- 
prinzip,’ pp. 17-18, 1903. 

** Morgan, T. H., “Evolution and Adaptation,” 1903. 

72 De Vries, in a recent paper (“Altere und Neuere Selektions- 
methode,” Biol. Centralbl., Vol. XX VI, pp. 385-395, 1906), describes 
the new methods of plant amelioration adopted by the Svalfor Ver- 
suchsstation (Sweden). These methods have been determined 
largely by the acceptance of De Vries’s mutations theory as a 
working hypothesis. 

* For account of the breeding and amelioration (artificial selec- 
tion) of plants see Darwin, ‘Variation of Animals and Plants 

Repeat (uuder Domestication,” many editions; Bailey, L. 
books and papers iz by “Plant-breeding,” 4th ed., 1900 ; Hays, W. M..,. 
on plant-breed- ‘‘Plant-breeding,” Bull. 29, Div. Veg. Phys. and 
mS Path, U. S. Dept. Agric, 1901; Webber, H. J., 
and Bessey, E. A., “Progress of Plant-breeding in the United 
States,” Yearbook of U. S. Dept. Agric., for 1889, pp. 465-490; 
Kellogg, V. L., “The Scientific Aspects of Luther Burbank’s Work,” 
Pop. Sci. Mo., pp. 363-374, Oct., 1906 (reprinted in Appendix to 
chapter ix of this book). 

*4 Pfeffer, Georg, “Die Umwandlung der Arten,” pp. 19-20, 1894. 

2° De Vries, H., “Species and Varieties, their Origin by Mutation,” 
pp. 798-826, 1905. 

*° Korschinsky, S., ‘“‘Heterogenesis und Evolution,” Naturwiss, 
Wochenschrift, Vol. XIV, p. 276, 1899. 

?™ Coe, C. G., “Nature versus Natural Selection,” 1894. A book 
devoted wholly to denying any validity at all to natural selection. 

*® Delage, Yves, “L’Hérédité,” 2d ed,, p. 4190, p. 843, 1903. 

** Morgan, T. H., “The Origin of Species through Selection Con- 
trasted with their Origin through the Appearance of Definite 
Variations,” Pop. Sci. Mo., pp. 54-65, May, 1905. 


CHAR Pika y.. 


DARWINISM ATTACKED (CONTINUED): THE 
THEORY OF SEXUAL SELECTION. 


THE differences between male and female individuals of 
a single species are often striking; recall the gorgeous 

et colouring, the plumes and tufts and tail-feathers 
sexual differ: Of many male birds compared with the sober 
eae and quiet plumage of their mates; the antlers 
of the stag, the mane of the lion and bison, the beard of 
the goat, many monkeys, and of man. Recall the mammee 
of the female quadrupeds, the brood pouches of the female 
kangaroos and opossums, the small size, compared with their 
mates, of many female birds, the winglessness of many fe- 
male insects. Other less familiar kinds of animals show 
sexual dimorphism or dichromatism in even more striking 
‘degree, while in many others the differences are less con- 
spicuous but nevertheless perfectly obvious if some attention 
is given to looking for them. These differences in size, 
colour, general appearances, and various specific structural 
details in head, trunk, wings, feet, plumage, etc., are over 
and beyond those primary radical differences existing in all 
species in which the two sexes are differentiated. Some of 
these differences may, however, have obvious relation to 
the primary differences, in that they may be connected im- 
mediately with the act of pairing or with the work of rear- 
ing the young. The presence in male insects of complexly 
developed holding organs, and in female mammals of milk 
glands exemplifies differences of this category. A great many 
sexual differences, however, have no such obvious direct 
relation to the function of producing and rearing the young. 

106 


DARWINISM ATTACKED. _ 107 


Such are the metallic purple and bronze colours of the male 
grackles compared with the dull brown of the females; the 
long tails and brilliant coloration of the male pheasants, 
the great, spreading, patterned tail of the peacock, the 
larger size or the winglessness of many female insects, etc. 
All these differences between male and female of the same 
species of animal, beyond or in addition to the differences 
between the actual primary reproductive organs, are known 
as secondary sexual differences, or the characters themselves, 
which may be characteristics of physiology and habit as 
well as the more familiar ones of structure, are called sec- 
ondary sexual characters. The layman may not readily 
appreciate the abundance and the great variety of these char- 
acters, but it is a fact that almost all species of animals, 
excepting those in the lower invertebrate branches, show 
them, and if one will try to recall the aspect of the two 
sexes in one after another of the species of animals with 
which one is familiar, mammals, birds, insects, etc., one will 
begin to realise how widespread and significant are these 
secondary sexual characters. ) 

Various biologists have made up classifications, from 
various points of view, of the different kinds of these char- 

Glassifiestiona 2CteTSs One classification, like that of Kramer * 
of secondary sex- for the secondary sexual characters of insects, 
ual characters: ay be based on the different parts of the body 
showing the differences between male and female indi- 
viduals, as head, antennz, thorax, wings, legs, abdomen, 
etc., and on the character of the differences themselves, as 
whether differences in structure or in colour and pattern. 
Another type of classification, and one more useful for our 
present discussion, is that based on the apparent significance 
or actual use of the differing characters. An excellent 
classification of this type is that of Plate.” The following 
are the principal subdivisions of this classification with a 
few examples illustrating each: 


108 DARWINISM TO-DAY. 
CLASSIFICATION OF THE EXTERNAL SECONDARY SEXUAL CHARACTERS. 


Group A. Characters which are useful to the possessor, or to its 
young, or have an indirect relation to reproduction. 

Sub-group 1. Specialisations in organs which aid in the finding of 
individuals of the other sex. Examples, the extra-develop- 
ment of the antenne in many male moths and beetles, the 
enlarged and divided eyes of certain flies and May-flies, the 
enlarged tactile feelers of male Daphnias, the larger or better 
wings of many male insects, the swimming membrane, in the 
breeding season, on the hind-legs of Molge parado.xa. 

Sub-group 2. Specialisations that aid in mating. Examples, the 
clasping organs of many male crabs, the hectocotylus of 
octopuses, the expanded tarsi of many male insects, and in 
general, the accessory copulatory organs of innumerable vari- 
ous animal species. 

Sub-group 3. Special size and form of the female due to the extra- 
development of the ovaries. Examples, in Psychid moths and 
parasitic Crustaceans. 

Sub-group 4. Differences connected with care of the young. Ex- 
amples, mammz of female mammals, brood-pouch of mar- 
supials, brood-sacs of male sea-horses, and brood-cavities in 
the back of male Pipa (a frog). 

Sub-group 5. Specialisations for defence or offence. Examples, 
protective coloration of female birds and insects, mimicry 
by female butterflies, antlers of the stag, strong canines of 
many male mammals (wild boars, etc.), sting of the female 
honey-bee, spurs of the cock, greater size and strength of 
many male mammals and birds. 

Sub-group 6. Differences in coloration which aid in the recogni- 
tion of the sexes (‘“‘recognition marks” of Wallace). 

Sub-group 7. Differences connected with various special habits of 
life. Examples, the pollen-baskets of the worker honey-bees, 
the winglessness of male fig-caprifying insects (Blastophaga), 
the large differences between males and females of certain 
insects where one sex lives parasitically, the other independ- 
ently, as the scale insects, the Strepsiptera, etc., the beak 
differences in the New Zealand bird, Heteralocha acutiros- 
tris, whose male chisels out the hard wood with a short, 
broad beak, while the female extracts insect larve from decay- 
ing wood by means of a long, curved beak. 

Group B. Exciting organs. These are found almost exclusively in 
the males only, and serve to indicate the sexual excitement 
of their possessors, and at the same time to stimulate or excite 


DARWINISM ATTACKED. 10g 


the females. The excitation of the male is manifest to the 
female through her senses of sight, hearing, and smell (in each 
case through one or more of these), and this perception gives 
rise reflexively to an excitation on the part of the female. 

Sub-group 1. The male characters may appeal to the sense of sight 
of the female: (a) by colours, as in the breeding plumage, or 
coloration, of many birds, fishes, amphibians, and reptiles, or, 
as in the constant brilliancy of colour and pattern in many 
butterflies, other insects, and spiders; or (b) by striking form, 
as the beard and hairy tufts of many monkeys and the 
extraordinary “horns” and processes of certain lamellicorn 
beetles ; or (c) by movable processes (often strongly coloured), 
as the wattles and movable feathers (tail, etc.) of certain birds, 
swelling cheek or neck sacs of turkeys, etc.; or (d) by strik- 
ing movements, as the dancing on the. ground or tumbling 
and whirling in flight of certain birds, the mating-time bat- 
tles of mammals, birds, and fishes, and the “‘love-dances” of 
spiders. 

Sub-group 2. The male characters appeal to the sense of hearing 
of the females, as the song of birds, the cries and calls of 
many mammals, frogs, and insects. ; 

Sub-group 3. The male characters appeal to the sense of smell of 
the females, as the odours given off by goats, chamois, musk- 
deer, beaver, etc., and from the scent-scales (androconia) of 
many male butterflies. 

Group C. Reciprocal organs; that is, organs which exist in func- 
tional condition in one sex but are inherited by the other only 
in rudimentary and often non-functional form. 

Examples; the reduced mammz of male mammals, the brood 
pouch of the male Thylacinus; wingless female butterflies often 
have a rudimentary sucking proboscis, which in some cases is in- 
herited by the males without any reduction of the wings; in 
cases of mimicry by female butterflies, the males often show 
some traces of the changed colour-pattern; traces of spurs in 
female pheasants, reduced horns of female antelopes and goats, 
small “horns” on female lamellicorn beetles, undeveloped stridu- 
lating apparatus in female crickets, katydids, etc. 

Group D. Indifferent characters, without any apparent utility. 

Sub-group 1. Rudimentary organs, which are wholly non-func- 
tional in one sex, although still functional in the other. 
Examples, the reduced wings of many female insects, the 
rudimentary alimentary canal of male Rotatoria. 

Sub-group 2. Negative characters, that is, those wholly failing in 
one sex, although present in the other. This lack can be a 


110 DARWINISM TO-DAY. 


primary one, that is, indicate an older phyletic condition, as 
the absence of antlers in the female deer; or be a secondary 
one, that is, gradually acquired by progressive reduction, as 
the loss of wings by many female insects. 

Sub-group 3. Atavistic characters, as the more marked hairiness 
on the breast of men as compared with women. 

Sub-group 4. Correlated characters, which may be called into ex- 
istence by other organs present; with the female mollusc 
Anodonta, the shell is more strongly bowed in adaptive 
correlation with the expanded brood chamber between the 
gills. 

Sub-group 5. A large number of secondary sexual characters 
which are incapable of specific classification, as the minute 
differences between the sexes in size and habitus; slight dif- 
ferences in wing form in humming-birds, dragon-flies, and 
butterflies; small differences in character and number of 
tarsal and antennal segments of many insects. 


As Plate justly remarks the foregoing classification can, 
of course, make no pretension to completeness. But it 

enrneks indicates sufficiently clearly certain important 
nificance ofthe differences among the secondary sexual char- 
Caron acters; differences especially important in con- 
nection with any attempt to get at an explanation of the 
why and how of these characters. Such a classification 
shows that many of these characters have uses which are 
of a kind directly helpful in the struggle for existence, as the 
strong antlers of the stags, useful in defence against attacking 
enemies ; the brood sacs of the kangaroos and opossum, use- 
ful in caring for their helpless young; the milk-glands and 
teats of all female mammals, the pollen-baskets and wax- 
glands of the honey-bee which make the workers more 
effective food-gatherers and food-storers, and the protective 
colours and patterns of many insects and birds. But others, 
many others, indeed, of these secondary sexual characters, 
are either of a kind apparently useless in the struggle for 
life, or even of a kind actually harmful. Of apparent useless- 
ness are the reduced wings of some male insects, and the 
host of slight differences in coloration, pattern, size, or 


DARWINISM ATTACKED. Il! 


shape, of different body-parts or of the whole body, the 
beards and hair-tufts of many male mammals and the combs 
and wattles of male gallinaceous birds. Of apparent harm- 
fulness are those ultra-developed pro-thoracic and head 
processes, “horns,” of stag and other lamellicorn beetles, the 
conspicuous staring colours of many male birds, the long 
dangling plumes, the weighty crests, and heavy dragging 
tails of others, all these parts also usually being dangerously 
conspicuously coloured. The lively loud song of many 
male birds, and the dancing and leaping of numerous male 
spiders and some male birds must also involve some danger 
to the performers by attracting the attention of their enemies. 
In fact most of those secondary sexual characters that are 
classified under the general head of “exciting organs” are 
apparently of a sort that should be actually disadvantageous 
in the struggle for existence. They are of a character tend- 
ing to make their possessors conspicuous and thus readily 
perceived by their carnivorous enemies. How is to be 
explained the existence of so many and such highly de- 
veloped structural and physiological characters of this kind, 
a condition that seems to stand in direct opposition to the 
theory of natural selection? Darwin’s answer to this ques- 
tion is contained in his theory of sexual selection. 
This theory, in few words, is that there is practically a 
competition or struggle for mating, and that those males are 
Darwin's the. Successful in this struggle which are the stron- 
ory ofsexual gest and best equipped for battle among them- 
comer icy selves, or which are most acceptable, by reason 
of ornament or other attractiveness, to the females. In the 
former case mating with a certain female depends upon 
overcoming in fight the other suitors, the female being the 
passive reward of the victor; in the second case the female 
is presumed to exercise a choice, this choice depending upon 
the attractiveness of the male (due to colour, pattern, plumes, 
processes, odour, song, etc.). The actual fighting among 


112 DARWINISM TO-DAY. 


males and the winning of the females by the victor, are ob- 
served facts in the life of numerous animal species. But a 
special sexual selection theory is hardly necessary to explain 
the development of the fighting equipment, antlers, spurs, 
claws, etc. This fighting array of the male is simply a special 
phase of the already recognised intra-specific struggle; it 1s 
not a fight for room or food, but for the chance to mate. 
But this chance often depends on the issue of a life-and- 
death struggle. Natural selection would thus account for 
the development of the weapons for this struggle. 

For the development, however, of such secondary sexual 
characters as ornament, whether of special plumage, colour, 
pattern, or processes, and song, and special odours, and 
“love-dancing,”’ the natural selection theory can in no way 
account; the theory of sexual selection was the logical and 
necessary auxiliary theory, and when first proposed by 
Darwin * met with quick and wide acceptance. Wallace in 
particular took up the theory and applied it to explain many 
cases of remarkable plumage and pattern development 
among birds. Later as he analysed more carefully his cases, 
and those proposed by others, he became doubtful, and 
finally wholly sceptical * of the theory. 

The theory as proposed by Darwin was based on the fol- 
lowing general assumptions, for the proof of each of which a 

Pree iitsa hue ato taany facts were adduced. First, many 
bases of the secondary sexual characters are not explicable 
sith by natural selection; they are not useful in the 
struggle for life. Second, the males seek the females for 
the sake of pairing. Third, the males are more abundant 
than the females. Fourth, in many cases there is a struggle 
among the males for the possession of the females. Fifth, 
in many.other cases the females choose, in general, those 
males specially distinguished by more brilliant colours, more 
conspicuous ornaments, or other attractive characters. 
Sixth, many males sing, or dance, or otherwise draw to 


DAKWINISMZATTACKED, \ 113 


themselves the attention of the females. Seventh, the sec- 
ondary sexual characters are especially variable. Darwin 
believed that he had observed certain other conditions to ex- 
ist which helped make the sexual selection theory probable, 
but the conditions noted are sufficient if they truly exist. 

Exposed to careful scrutiny and criticism—an admira- 
ble and convincing example of such scientific and impar- 
tial criticism is Kramer’s analysis of the 
Scrutiny and ; 
criticism of the Secondary sexual characters of European in- 
Stee sects—the theory (@f sexual selection has been 
relieved of all necessity of explaining any but two categories _ 
of secondary sexual characters, namely the special weapons 
borne by males, and the special ornaments and excitatory 
organs of the males and females. For examination has 
disclosed the fact that males are not alone * in the possession 
of special characters of attraction or excitation. Regarding 
these two categories Plate,° in his able recent defence of 
Darwinism, says, “the first part of this theory, the origin of 
the special defensive and offensive weapons of males through 
sexual selection is nearly universally accepted. The second 
part of the theory, the origin of exciting organs has given 
rise to much controversy. Undoubtedly the presumption 
that the females compare the males and then choose only 
those which have the most attractive colours, the finest song, 
or the most agreeable odour, presents great difficulties, but 
it is doubtful if it is possible to replace this explanation 
by a better.” Some of these difficulties may be briefly 
enumerated. 

The theory can be applied only to species in which the 
males are markedly more numerous than the femaies, or in 

which the males are polygamous. In other 

Males must be , 
morenumerous Cases there will be a female for each male 
eens whether he be ornamented or not; and the 

unornamented males can leave as many progeny 

as the ornamented ones, which would prevent any cumula- 


114 DARWINISM TO-DAY. 


tion of ornamental variations by selection. As a matter of 
fact in a majority of animal species, at least among the 
vertebrates, males and females exist in approximately equal 
numbers. 

Observation shows that in most species the female is 
wholly passive in the matter of pairing, accepting the first 

Femaleis usu. Male that offers. Note the cock and hens in 
ally passive. the barnyard. 

Ornamental colours are as often a characteristic of males. 
of kinds of animals in which there is no real pairing, as 

Oe nares Sans those which pair. How explain by 
cur on males that Sexual selection the remarkable colours in the 
eeu bare breeding season of many fishes, in which the 
female never, perhaps, even sees the male which fertilises. 
her dropped eggs? 

Choice on a basis of ornament and attractiveness implies 
a high degree of zsthetic development on the part of the 

females of animals for whose development in 

Assumption of re ; 
esthetic develop- this line we have no (other) proof. Indeed this 
mentinlower choice demands esthetic recognition among 
animals. q : es 

animals to which we distinctly deny such a 

development, as the butterflies and other insects in which 
secondary sexual characters of colour, etc., are abundant 
and conspicuous. Similarly with practically all invertebrate 
animals. Further, in those groups of higher animals where 
esthetic choice may be presumed possible we have repeated 
evidence that preferences vary with individuals. Certainly 
they do with man, the animal species in which such prefer- 
ences certainly and most conspicuously exist. In some 
human races hair on the face is thought beautiful; in others, 
ugly. Besides even if we may attribute fairly a certain 
amount of zsthetic feeling to such animals as mammals and 
birds, is this feeling to be so keen as to lead the female 
to make choice among only slightly differing patterns of 
songs? Yet this assumption is necessary if the development. 


DARWINISM ATTACKED. 115 


of ornament and other attracting and exciting organs is to 
be explained by the selection and gradual cumulation through 
generations of slight fortuitously appearing fluctuating 
variations in the males. 

There are actually very few recorded cases where the 
observer believes that he has noted an actual choice by a 

ial hated female. Darwin records eight cases among 
cases of choice birds. Since Darwin not more than half a 
i ae dozen other cases, all doubtful, have been 
recorded. Also a few instances, all more illustrative of 
sexual excitation of females resulting from the perception 
of odour or actions, than any degree of choice by females, 
have been listed. , 

In numerous cases the so-called attractive characters of 
the males, described usually from preserved (museum) 

specimens, have been found, in actual life, to 

Some so-called 
attractive char- be Of such a character that they cannot be noted 
acters not visible hy the female. For example, the brilliant 
in nature. : 

colours and the curious horns of the males 

of the dung beetles are, in life, always so obscured by dirt 
and filth that there can be no question of display to the 
female eyes about them. The dancing swarms of many 
kinds of insects are found to be composed of males alone 
with no females near enough to see; it is no case of an 
excitatory flitting and whirling of many males before the 
eyes of the impressionable females. Of many male katy- 
dids singing in the shrubbery will not for any female that 
particular song be the loudest and the most convincing that 
proceeds from the nearest male, not the most expert or the 
strongest stridulator? Similarly with the flitting male fire- 
flies; will not the strongest gleam be, for any female, that 
from the male which happens to fly nearest her, and not 
from the distant male with ever so much better, stronger 
light? 

Stolzmann finds it difficult to understand, when nearly 


116 DARWINISM TO-DAY. 


related species differ widely in their ornamental plumage, 
that this should be attributed to a difference in 
Problem of preference among the females of the related 
the Andean . ; ‘ : 
humming-birds, Species. The humming-bird, Schistes perso- 
natus, lives in Ecuador on the west side of the 
Andes, in a restricted range of four degrees of latitude. It 
is distinguished from the nearly related Schistes geoffroy 
especially in the possession by its male of a brilliant spot over 
each eye. Schistes geoffroyi lives on the east side of the 
Andes from Colombia to Central Peru, with a range cover- 
ing over twenty degrees of latitude, which range is divided 
into two completely separated regions by the Maranon 
valley. Now if isolation alone is sufficient to produce a 
change in the taste of the females, one would expect to find 
two sorts of males (as far as ornamental pattern goes) in- 
side this one species. But there is but one kind of male 
through the whole range. Why is the taste of the female 
constant through twenty degrees of latitude, while it is 
changed on the other side of the Andes in a limited range 
of four degrees of latitude? Another case presented by 
Stolzmann is even more striking. The Chilian hummer, 
Eustephanus galeritus, which is green in both sexes, has 
migrated from the continent to the Juan Fernandez Islands. 
On Masatierra Island it has changed to Eust. fernandensts, 
in Masafuera Island to Eust. leyboldi. These two species 
agree in the females with the original continental form 
(that is, are green) while the males have become red, but in 
different pattern in the two species. Eust. galeritus (the 
Continental form) also occurs on Masatierra Island, in the 
same form as on the continent, that is, with green male. 
Now one must presume from this state of affairs that this 
species (galeritus) has been able to reach Masatierra twice, 
once long ago—the descendants of the invasion having 
changed to Eust. fernandensis—and once more recently— 
the descendants of these later migrants showing as yet no 


DARWINISM ATTACKED. 117 


sign of a transformation of the malecolour. Shall one in this 
case and others like it, asks Stolzmann, assume a change of 
beauty-ideal on the part of the females? Much simpler and 
much more reasonable, according to Stolzmann, is it to see in 
the change of colour of the males of the earlier migrants the 
results of the direct influence of the new environment; the 
islands are distinctly milder and warmer than the continent. 

Even if the females do choose among the males on a basis 
of attractiveness, how are the characters of the more at- 

tractive males to become especially fostered 

How are more ; 

attractive char- and accumulated by selection? Do such males 
acters to be produce more offspring or more vigorous ones 
fostered ? : : 

than the other males, which, though rejected 
by the first females, find their mates among the females not 
already mated? Are we to attribute to the more ornamental 
males a particular vigour? If so, may not that very vigour 
be the cause of the extra-production of colour or plumage 
or wattles, etc.? 

Darwin admits, in order to explain the beginnings of 
colour and ornament development, a certain degree of differ- 

_., ence between the male and female in regard to 
Darwin’s sig- : : ‘ . 
nifcantadmis- their reaction to environmental influences. If 
sion, so, may not these admitted differences be really 
sufficient to account for even a pretty high degree of differ- 
ence in development of secondary sexual characters? 

The special display of colours, tufts, plumes, spreading 
tails, and other secondary sexual characters by the males at 
mating time is an observed fact; the “dances” 
of cranes and storks, the serenades of the song- 
birds, the evolutions of the male spiders are all 
familiar phenomena in the mating season of these animals. 
And they probably do exercise an exciting effect on the 
females, and are probably actually displayed for this pur- 
pose. But does this in any way prove, or even give basis 
for a reasonable presumption for belief in a discriminating 


Does display 
prove choice ? 


118 DARWINISM TO-DAY. 


and definitive choice among the males on the part of the 
female? And it is this actual choosing which is the neces- 
sary basis for the theory of sexual selection. 

How explain the well-known cases of a similar extra- 
development of plumage in the nuptial season by both 

Heeerpien males and females, as in certain herons and 
ae in other birds? And what of those other cases in 
common to both Which it is the female that is the brighter-col- 
sexes 7 oured individual of the pair? To explain the lat- 
ter case Darwin assumes that in these cases the males have 
done the selecting, but even this rather too easy reversal of 
the situation postulated as a fundamental generalisation 
of the theory does not explain the first of the questions in 
this paragraph. Do both sexes among the herons do 
selecting? 

Morgan" lists twenty objections to the sexual selection 
theory, several of which are identical with those already 

mentioned in the foregoing paragraphs, but 

Morgan’s list among which are several to which we have not 

of objections, : 
referred. One of these is that “some of the 

objections that apply to the theory of natural selection 
apply also with equal force to the theory of sexual selection 
in so far as the results in both cases are supposed to be the 
outcome of the selection of individual, or fluctuating, varia- 
tions. If these variations appear in only a few individuals, 
their perpetuation is not possible, since they will soon dis- 
appear through crossing. It would be, of course, preposter- 
ous to suppose that at any one time only those few indi- 
viduals pair and leave descendants that have secondary 
sexual characters developed to the highest point, but if 
something of this sort does not occur, the extreme of 
fluctuating variations cannot be maintained. Even if half 
of the individuals are selected in each generation, the ac- 
cumulation of a variation in a given direction could not go 
very far. The assumption, however, that only half of all 


DARWINISM ATTACKED. 11g 


the individuals that reach maturity breed, and that all of 
these are chosen on account of the special development of 
their secondary sexual characters, seems preposterous. 
Furthermore, if it is assumed that the high development of 
the new character appears in a large number of individuals, 
then it is not improbable that its continued appearance might 
be accounted for without bringing in, at all, the hypothesis 
of sexual selection.” 

Again, Morgan well points out that “the development, or 
the presence, of the esthetic feeling in the selecting sex is not 
accounted for on the theory. There is just as much need to 
explain why the females are gifted with an appreciation of the 
beautiful as why the beautiful colours develop in the males. 
Shall we assume that still another process of selection is go- 
ing on, as a result of which those females are selected by the 
males that appreciate their unusual beauty, or that those 
females whose taste has soared a little higher than that of the 
average (a variation of this sort having appeared) select 
males to correspond, and thus the two continue heaping 
up the ornaments on one side and the appreciation of these 
ornaments on the other? No doubt an interesting fiction 
could be built up along these lines, but would any one be- 
lieve it, and if he did, could he prove it? 

“Darwin assumes that the appreciation on the part of 
the female is always present, and he thus simplifies, in 
appearance, the problem, but he leaves half of it un- 
explained. x 

“There is another side to the question,” also says Morgan, 
“the importance of which is so great, that it is surprising 
that Darwin has not taken any notice of it. If, in order to 
bring about, or even maintain, the results of sexual selection, 
such a tremendous elimination of individuals must take 
place, it is surprising that natural selection would not 
counteract this by destroying those species in which a 
process, so useless for the welfare of the species, is going 


120 DARWINISM TO-DAY. 


on. It is curious that this has not been realised by those 
who believe in both of these two hypotheses. 

“What has just been said applies also with almost equal 
force to the development of such structures as the horns 
of the deer, bison, antelopes, and the brilliant colours of 
many insects and birds. If in nature, competition between 
species takes place on the scale that the Darwinian theory 
of natural selection postulates, such forms, if they are much 
exposed, would be needlessly reduced in numbers in the 
process of acquiring these structures. So many individuals 
would have been at such a disadvantage in breeding, that 
if competition is as severe as the theory of natural selection 
postulates, these species could hardly be expected to compete 
successfully with other species in which sexual selection was 
not taking place.” 

’ Finally to make an end of miscellaneous objections and 
come to that one which promises to be, if it is not already, 
the most serious obstacle in the way of the 
Experimental : yore 

evidence is op- S€Xtal selection theory, it is a fact that all the 
posed tosexual evidence (though it be little as yet) based on 

selection theory, ; : 
actual experiment is strongly opposed to the 
validity of the assumption that the females make a choice 
among males based on the presence in the males of ornament 
or attractive colours, pattern, or special structures. I may 
mention especially the striking experiments of Mayer * 
(which, published in a small entomological journal of 
limited circulation, have not received the attention that they 
deserve) on the large Bombycine moth, Callosamia pro- 
methea. This well-known American moth expands about 
three and one-half inches and shows unusually pronounced 
secondary sexual differences as to colour and pattern. The 
females are reddish-brown in ground colour, while the males 
are blackish and in the two sexes the pattern is distinctly 
different. If there is any moth species in which the colours 
and general pattern of the male ought to be readily obvious 


DARWINISM ATTACKED, I2L 


to the female, and in which sexual selection might be pre- 
sumed to have been the influence in producing a pronounced 

ee male type of preferred pattern, it As this 
perimentson Species. Mayer’s simple and convincing ex- 
Sear periments were as follows: Mayer took four 
hundred and forty-nine pupze (in cocoons) of the moth 
Callosamia promethea, which had been collected*in Massa- 
chusetts and New Jersey, south to Loggerhead Key in the 
Dry Tortugas Islands off Florida. This island is separated 
by many miles of ocean from other land, and is hundreds 
of miles south of the range of the species. Evidently no 
interference with Mayer’s experiments could come from 
outside individuals of this species. The moths issued during 
May and June in the proportion of about two males for 
each female. The males of this species seek out the female 
for pairing and can do this for a considerable distance. As 
many as several dozen males will find a single female and 
hover, fluttering, about her. Mayer’s first experiments were 
directed to the end of determining if the males found the 
females by sight or by smell. By enclosing females in 
numerous jars variously arranged and covered or uncovered, 
it was readily determinable that males never pay any 
attention to females enclosed in transparent jars so closed 
as to prevent the escape of any odours from the female, 
while to females enclosed in boxes or wrapped in cotton so 
as to be invisible but yet capable of giving odour off into 
the air males came promptly and hovered about. To locate 
the organs of scent in the female Mayer cut off abdomens 
from various females and then placed abdomens and ab- 
domenless females at some little distance apart. Males 
came to the abdomens and not to the thorax plus wings, 
legs, and head parts. Females were proved to increase in 
attractive power with age, and virgins are a little, but only 
a little, more attractive than already fertilised females. It 
was readily proved, by experiments with males whose an- 


122 DARWINISM TO-DAY. 


tennz were covered with shellac, photographic paste, glue, 
paraffin, etc., that the sense of smell is seated in the antenne. 
Males with antennze covered with photographic paste did 
not find females, while the same males with this paste dis- 
solved off did. 

Mayer now tried to test the selective action of the female. 
The male promethea has blackish wings while the females 
are reddish-brown. In accordance with the theory of 
sexual selection, the peculiar coloration of the male should 
be due to the selection of dark-coloured males, so that 
under this influence the males would become, in successive 
cenerations, darker and darker until the present coloration 
has been attained. Mayer’s own account of his experi- 
ments and conclusions to test the preferences and selective 
action of the females is as follows: 

“In order to test this hypothesis I cut off the wings of a 
number of females, leaving only short stumps, from which 
all the scales were carefully brushed. Male wings were 
then neatly glued to the stumps, and thus the female pre- 
sented the appearance of a male. Under these circum- 
stances the males mated with the female quite as readily as 
they would have done under normal conditions. 

“I then tried the experiment of gluing female wings upon 
the male. Here again the mating seemed to occur with 
normal frequency, and I was unable to detect that the 
females displayed any unusual aversion toward their 
effeminate-looking consorts. 

“It is also interesting to note that normal males pay no 
attention to males with female wings. 

“In another series of experiments the wings were cut 
entirely off of males and females and the scales brushed 
off their bodies; and yet these shabby males were readily 
accepted by normal females, nor could I see that normal 
males displayed any aversion to mating with wingless 
females. 


DARWINISM ATTACKED. 123 


“We are therefore forced to conclude that the melanic 
coloration of the male has not been brought about through 
the agency of sexual selection on the part of the female.” 

More recently Mayer (and Soule) ° repeated these experi- 
ments on a more extensive scale and with some variations 

aneuet in character. Fifteen hundred cocoons of 
Soule’s experi- © Promethea were collected in the winter of rgo1- 
a o2 and hung in trees so that the issuing moths 
might fly about unconfined. ‘About six hundred males 
emerged from the cocoons and the wings of about one-half 
of them were painted with scarlet or green ink, while the 
others were allowed to remain normal in colour. It was 
evident that the males whose wings were scarlet and green 
succeeded fully as well in their attempts to mate as did the 
normal males.” 

Experiments were also tried with the moth Porthetria 
dispar, in which the male is brown and the female white. 
The experiments showed that males with wings painted 
scarlet or green were accepted as readily as normal males, 
but that males with the wings cut off were more apt to meet 
with resistance from the females than perfect males were. 
From these experiments Mayer and Soule conclude that the 
mating instinct in the males of C. promethea and P. dispar 
is a phenomenon of chemotaxis. Sexual selection on the 
ground of colour alone does not affect it, and there is no 
associative memory connected with it. 

To these experiments may be added the observations of 
Douglass,” who found that females of the wall-lizard, 
Lacerta muralis, showed no preference what- 
ever among the variable patterns exhibited by 
males in breeding-coat. Dutrigen** observed 
that male lizards without tails are accepted readily by 
females. 

Finally, also, of the nature of objections to the sexual 
selection theory are the replacing or substutionary explana- 


Experiments 
on lizards. 


124 DARWINISM TO-DAY. 


tions of secondary sexual characters which various biol- 
ogists have offered. These explanations will be presented 

Alternative ex- in some detail in chapter xi, which is devoted 
ech to an exposition of the various alternative 
characters. theories proposed to replace or partially to re- 
place the Darwinian theories. It must be sufficient to say here 
that the theories proposed to account for secondary sexual 
characters mostly rest on one or both of two principal basic 
assumptions; first, that the secondary sexual characters are 
produced as the result of the immediate stimulus (naturally 
different) of the sexually differing primary reproductive 
| organs, this stimulus being usually considered to result 
from an internal secretion of the genital organs acting on 
certain tissues of the organism; and, second, that the males 
in most species possess an excess of energy which manifests 
itself in extra-growths, extra-development of pigment, 
plumage, etc., and that displays by the males of special move- 
ments, sound-making, etc., are direct effects or manifesta- 
tions of sexual excitation. To these explanations should be 
_ added the rather far-fetched one of Emery, who believes that 
many cases of secondary sexual differences are explained by 
| the sudden appearance (mutation) of another form of male 
or female, the persistence for a while of the two forms side 
by side, as now exists in numerous dimorphic species (espe- 
cially among insects), and then the gradual dying out (kill- 
ing out by natural selection) of one of the two old original 
forms (the one like the other sex), thus leaving the other, 
or aberrant form. The ideas of Cunningham,’* who does 
not believe that any selection of fortuitous variation can 
account for secondary sexual characters, may also be re- 
ferred to. In a book of over three hundred pages this 
author lists and describes—according to principal animal 
groups—a host of secondary sexual characters, and pro- 
poses a theory to account for them. ‘‘The direct effects,” 
writes Cunningham, “of regularly recurrent stimulations are 


a a 


DARWINISM ATTACKED. 125 


sooner or later developed by heredity, but only in associa- 
tion with the physiological conditions under which they were 
originally produced. This is the explanation of the limita- 
tions of particular modifications not merely to particular 
species or kinships, but to particular periods in the life of 
the individual, to a particular sex and even to a particular 
season of the year in that sex.” The author believes that an 
examination of secondary sexual characters shows that they 
develop at places and in parts which are at the time of 
sexual excitement unusually directly stimulated by exertion 
or contact or use. These secondary sexual characters are 
“in many cases not merely limited to the period of mature 
life but actually to that part of the year in which the repro- 
ductive organs are active, that is to-the breeding season.” 
In closing this chapter given up to objections to the Dar- 
Winian theories of natural and sexual selection, attention 
may be called to Wolff’s ** objection to natural 
Importance of selection based upon the dependence of the na- 
the sexual selee- tral selection theory on the sexual selection 


tion theory as a 
support ofthe theory for explanation of the existence of orna- 
natural selection 
theory. mental characters, and of all these secondary 

sexual characters, which are useless or even 
apparently disadvantageous in the life-and-death inter- 
specific struggle for space and food. As Wolff looks on the 
sexual selection theory as wholly discredited, he finds this 
necessary dependence on it by believers in natural selection 
for the explanation of those characters just mentioned 
strong evidence for the weakness of the natural selection 
theory. 

APPENDIX. 


* Kramer, Paul, “Theorie u. Erfahrung; Beitrage zur Beurtheilung 
des Darwinismus,” 1877, Halle. An interesting paper criticising 
the selection theories from two points of view; first, on the basis of 
a mathematical treatment of the Darwinian hypothesis (especially 
that of sexual selection), the author taking Darwin’s premises and 
by a mathematical handling of them showing that they do not lead 


126 DARWINISM TO-DAY. 


to the Darwinian conclusions; and, second, on a basis of the care- 
ful scrutiny of the facts of secondary sexual differences, the author 
finding sexual selection wholly unable to account for the great 
majority of secondary sexual characters among animals. 

> Plate, L., “Uber die Bedeutung des Darwin’schen Selections- 
prinzips,” pp. 107-111, 2d. ed., 1903, Leipzig. 

* Darwin outlined the theory of sexual selection in the “Origin 
of Species” (1859), but first treated it at length in the ‘‘Descent of 
Man UParts Ll and 111), 1878 

* Wallace, A. R., ‘“Tropical Nature,” chap. v, 1878; and “Darwin- 
ism,” chap. x, 1891, London. 

° Doane (Ent. News, Vol. XVIII, pp. 136-138, 1907) has described 
the striking behaviour during mating of certain Dolichopodid flies 
(Scellus virago, n. sp.) observed by him on the salt marsh flats 
of San Francisco Bay, near Stanford University. In these matings 
it is the female which is the active sex in pursuing and exciting 
the other. 

* See note 2. 

"Morgan, T. H., “Evolution and Adaptation,” chap. vi, 1903, 
New York. This chapter is an exhaustive attack on the theory of 
sexual selection. 

® Mayer, A. G., “On the Mating Instinct in Moths,” Psyche, Vol. 
IX, pp. 15-20, 1900. 

®* Mayer, A. G., and Soule, C. G, “Some Reactions of Cater- 
pillars and Moths,” Jour. Exper. Zool., Vol. III, pp. 427-431, 1906. 

*°? Douglass, N. G., “On the Darwinian Hypothesis of Sexual 
Selection,” Nat. Science, Vol. VII, pp., 398-406, -1895. 

™ Durigen, ‘““Deutschlands Amphibien u. Reptilien,” p. 89, 1897. 

*? Cunningham, J. T., “Sexual Dimorphism in the Animal King- 
dom,” 1900. 

*® Wolff, Gustav, ‘‘Beitrage zur Kritik der Darwin’schen Lehre,” 
p. 21 ff., 1898, Leipzig. A bitter but keen and trenchant critical ex- 
position of certain weaknesses in the selection theories. He criti- 
cises the theory of sexual selection in the following words: 

“An diese Falle reiht sich vielleicht am besten die Betrachtung 
der Folgen, welche frithzeitige Sterilitat auf die Ausbildung von 
sekundaren Geschlechtscharakteren austibt. Wir k6n- 


Wolff's exposi- : : : ; : 
tion of weak- nen ja diese Erscheinungen auch in gewissem Sinne 
nesses in sexual zu den Riickbildungen rechnen; sie haben aber insbe- 
selection. sondere auch das mit den vorigen Fallen gemeinsam, 


dass wir hier ebenfalls einen im individuellen Leben des Organismus. 
sich abspielenden Vorgang beobachten konnen, der nach der Selek- 
tionstheorie nicht eintreten durfte. 

“Nach der Selektionstheorie entstehen ja sekundare Geschlechts- 


DARWINISM ATTACKED. he, 


merkmale dadurch, dass eben Individuen des einen Geschlechts, bei 
welchen durch zufallige Variierung eine Andeutung solch eines. 
Merkmals da war, mehr Chancen hatten, sich fortzupflanzen und 
diese Eigentumlichkeit auf die Nachkommen ihres Geschlechts zu 
vererben, von denen dann durch den gleichen Prozess immer 
diejenigen zur Fortpflanzung ausgewahlt wurden, welche die betref- 
fende Eigentiimlichkeit am starksten besassen. Es soll also zwischen 
jenen Gebilden und dem Geschafte der Zeugung an und fir sich 
nicht der geringste Zusammenhang existieren. Dann ist aber 
schwer erklarlich, warum jene sekundaren Geschlechtsmerkmale 
sich haufig nur zur Zeit der Geschlechtsthatigkeit bilden und nachher 
wieder verschwinden, wie z. B. der Hochzeitskamm der Tritonen. 
Aber geben wir einmal zu, das sei bloss ein zufalliges Zusammen- 
treffen, indem eben diejenigen zur Fortpflanzung gelangten, welche 
gerade zufallig um die Zeit der Brunst eine bald wieder zufallig 
verschwindende Verstarkung des Kammes besassen. Es ist zwar 
unmdglich, sich dies, insbesondere das Verschwinden des Kammes,. 
vorzustellen, weil ja, wenn auch das spatere Verschwinden des: 
Kammes dem Tiere irgend einen Vorteil gebracht haben sollte, 
dieser bei der Selektion in keiner Weise sich geltend machen konnte, 
oder doch nur in Bezug auf das Individuum aber nicht auf dessen 
Nachkommen, aber nehmen wir einmal an, das sei alles in Ordnung:. 
wie erklart sich dann, dass, z. B. beim kastrierten Hirsch kein 
Geweih sich entwickelt, dass der kastrierte Mensch hohe Stimme 
behalt, keinen Bart bekommt u. s. w., u. s. w.? 

“Auch andere Ruckbildungen, welche nach Aufh6ren der Ge- 
schlechtsthatigkeit normal sich einstellen (z. B. Aufhoren der Flim- 
merbewegung im Uterus des Weibes nach Aufhoren der Menstrua- 
tion, Verlust der Flugel nach der Begattung bei Insekten,* etc.), bieten 
der Selektion die grossten Schwierigkeiten, denn wenn hier die 
Rickbildung einen Vorteil b6te, welcher die Auswahl der Indi- 
viduen, bei welchen diese Rtickbildung auftrat, herbeiftihrte, so 
konnte dieser Selektionsprozess doch erst nach der Fortpflanzungs- 
zeit eintreten, auf die nachfolgenden Geschlechter daher von keinem. 
Einflusse mehr sein. 

“Der unbestreitbare Zusammenhang, welcher zwischen der Ge- 
schlechtsthatigkeit und den sekundaren Geschlechtsmerkmalen 
besteht, ist nun aber nicht etwa durch das Wort ‘Korrelatioz” 
erklart. Es ist natitirlich richtig, dass eine Anderung irgend eine 
andere im Gefolge haben kann, dass es also korrelative Abande- 
rungen giebt, aber ist denn damit vielleicht erklart, dass eine: 
bestimmte zweckmassige Abanderung nun auch eine andere ftr 


*In diesem letzteren Fall ist vielleicht doch ein Vorteil ftir die 
Art durch Vermittlung der Brutpflege denkbar. 


128 DARWINISM TO-DAY. 


den jeweilig vorliegenden ganz speziellen Fall ntitzliche Abande- 
rung bedingt? Korrelative Abanderungen beziehen sich ja in den 
meisten Fallen, wo wir von solchen sprechen, auf ganz bestimmte 
Verhaltnisse der Aussenwelt. Sich zur Erklarung solcher Erschein- 
ungen mit der Konstatierung eines, Gesetzes der Korrelation 
zufrieden geben, heisst einfach eine praestabilierte Harmonie 
zwischen der Entwicklung der Organismen und den Verhaltnissen 
der Aussenwelt annehmen. Das Ratselhafte ist ja zunachst nicht 
der Umstand, dass es tiberhaupt Korrelationserscheinungen giebt 
(wenngleich wir nattirlich auch hierftir ebensowenig, wie 
fir irgend eine andere Lebenserscheinung eine Erklarung haben), 
sondern der Umstand, dass eine Eigenttimlichkeit eine andere 
korrelativ im Gefolge hat, die eben gerade ftir besondere 
aussere Zwecke vorteilhaft ist. Hier kann die Selektionstheorie 
nichts ausrichten, denn der Selektionsprozess hat doch keinen Fin- 
‘fluss auf die Variierungsgesetze, zu welchen die Korrelationsge- 
setze gehoOren; diese mtissen vielmehr vorausgesetzt werden. 

“Es giebt ttbrigens Thatsachen, die mir darauf hinzudeuten schei- 
nen, dass die korrelativen Bezi¢hungen noch viel verwickelter sind, 
und dass korrelative Beziehungen gar nicht immer auf die Ent- 
stehung korrelativer Abanderungen zuriickzufthren sind, sondern 
dass, was ja noch viel ratselhafter ist, eine Korrelation erst sekundar 
erworben werden kann, wie folgendes Beispiel zeigen dirfte. 

“Von den drei verschiedenen Individuen des Bienenstaates hat 
nur die Arbeitsbiene an der Innenflache des Tarsus regelmassige 
Borstenreihen, sogenannte Burstchen. Da die Arbeitsteilung immer 
eine hodhere Differenzierung ist, so kann es keinem Zweifel unter- 
liegen, dass urspriinglich bei allen Formen die Beine gleich waren. 
Kaum zu entscheiden dtirfte wohl die Frage sein, ob urspriinglich 
sich die Burstchen sowohl bei mannlichen als auch bei weiblichen 
Individuen differenzierten, sodass das Fehlen derselben bei den 
Drohnen als Rtickbildung betrachtet werden miusste, oder ob die 
Birstchen gleich von vornherein als sekundares Geschlechtsmerkmal 
der Weibchen auftraten. Im erstern Fall ware also die Bildung 
primar in keinerlei Korrelation zum Geschlechtsapparate gestanden, 
diese mtsste vielmehr erst spater erworben worden sein. Im 
zweiten Fall waren die Burstchen als zum Geschlechtsapparate 
korrelative Bildungen entstanden, aber in beiden Fallen musste 
eine Anderung des Korrelationsverhaltnisses eingetreten sein, die 
Korrelation musste namlich eine reziproke werden: die Entstehung 
von Burstchen ist zwar an das weibliche Geschlecht geknupft, 
jedoch in der Weise, dass die Biirstchen nur auftreten, wenn die 
Geschlechtsorgane nicht zur Ausbildung kommen.” 


CEAR PIR EY I: 
DARWINISM DEFENDED. 


In taking up the defence of Darwinism it should be noted 
in the first place that the anti-Darwinians are without the 
walls; that theirs is the burden of attack; that 


Advantageous ; : ; P 
position ifthe. against them is the presumption of right. The 
defenders of Darwinians are in the castle, theirs simply the 
Darwinism. . 


necessity of withstanding or repelling really 
significant and truly threatening attack; theirs the strength 
of possession and the presumption of truth. Much anti- 
Darwinism is futile and easily answered; much was an- 
swered by Darwin * himself before ever the anti-Darwinians 
formulated it ; much other anti-Darwinism is directed against 
a position which Darwinism, true Darwinism, has long seen 
the inadvisability, indeed the impossibility, of holding. 
With certain concessions made, what use of further struggle 
over them? Thus by answering briefly the insignificant and 
undamaging part of anti-Darwinian attack, or by referring 
to Darwin’s own answers of this, and by indicating clearly 
and definitely the concessions that Darwinism is ready to 
make, has made, indeed—these humiliating concessions, if 
humiliation is in them, only being made necessary because 


*Darwin’s anticipation of the criticisms of his theories, and his 
own open-minded and detailed answers to these criticisms, should, 
of course, be held clearly in mind by any student of fitir-und- 
gegen Darwinismus, but many of these answers concern objections 
which present-day Darwinism has largely conceded as valid, and 
most of the others touch matters on which modern biological re- 
search has thrown much new light. So that it is perhaps fairer 
to the Darwinian theories to set out the attitude of present-day 
Darwinians, For a detailed critical consideration of Darwin’s own 
answers, see Morgan, “Evolution and Adaptation” (1903). 


129 


130 DARWINISM TO-DAY. 


of the ill judgment and rash enthusiasm of certain too 
ardent and too conspicuous friends of Darwinism, the so- 
called neo-Darwinians—with this salutary restriction of 
diffuseness in account, “Darwinism Defended” may be con- 
fined to fewer pages than have been devoted to “Darwinism 
Attacked” without suggesting by-this brevity any necessary | 
weakness in the Darwinian position. 

Let us give our first attention to the Darwinian conces- 
sions—those concessions which the biological world has 

see Hi practically agreed have been made necessary by 
against ultra- the steady criticism of the exaggeration and 
Darwinism, magnification, almost wholly post-Darwinian in 
appearance, of the Darwinian factors in evolution. It is 
strange, but wholly true, that the modern reaction and revolt 
against Darwinism is chiefly due to the activity and attitude 
taken by certain of its over-ardent friends. Weismann, by 
denying validity to any other evolutionary factor than the 
natural selection of purely congenital variations, and by the 
development to an illogical and untenable extreme of his 
theory of the independence and continuity of the germ- 
plasm, precipitated the revolt and furnished the enemy with 
the very weapons needed to- overcome neo-Darwinism. 
The evolution champion Haeckel, although not at all a 
Weismannian Darwinian, has also by his daring and reck- 
less speculative development of certain phases of evolution- 
ary thought, especially in its relation to sociology and 
religious philosophy, and by his obstinate adherence to, and 
reiteration of, certain long discredited more strictly biological 
dogmas of evolutionary science, contributed to 
produce an irritation and antagonistic activity 
among biologists, especially in Germany, which has helped 
make many friends for the anti-Darwinian party. “Der 
Haeckelismus in der Zoologie,’* as Semper originally 
phrased it, is the object of a curiously bitter and often- 
expressed contempt in German biological circles. I fancy 


Haeckel. 


DARWINISM DEFENDED. 13I 


that this feeling really depends not so much on Haeckel’s 
attitude and speculative writing in zoology as in his unpar- 
donable intrusion into politics and religion; the Social- 
Democrats and the Free-Thinkers have found a helpful and 
willing scientific champion in Haeckel. And this is sin 
superlative in rigorous minds! As a matter of fact, how- 
ever, biologists generally are agreed that Haeckel’s daring 
speculations and reckless progress in advance of positions 
grounded on observed fact have been, in a way, always repre- 
hensible and dangerous to the fair fame of biological science. 
But, to my mind, biologists may also fairly agree that this 
very activity and speculative daring of Haeckel have in- 
spired much genuine biological investigation (for the sake 
of denying or confirming his speculations) and have led to 
a salutary reactionary critical attitude toward other biologi- 
cal speculations and hypotheses. It is a rare ism in any 
science or philosophy that yields nothing good. 

Weismannism is wholly different from Haeckelism. It 
has only in common with it that it is, in part, also daringly 
speculative. But the speculations primarily interest neither 
Free-Thinkers nor Social-Democrats. They have to do 
with the ultimate structure and behaviour of protoplasm, 
especially germinal protoplasm, and with the intimate proc- 
esses of heredity and variation. 

Weismann first attempted to free Darwin’s general theory 
of modification and species-forming from all taint of La- 
marckism; an attempt which resulted in his 
apparently successful overthrowal of the com- 
monly accepted theory of the inheritance of 
acquired characters, a theory or assumption which is a 
fundamental and indispensable part of the general Lamarck- 
ian theory. .(Lamarckism and the inheritance of acquired 
characters are explained and briefly discussed in chapter x of 
this book.) On the strength of this success Weismann pro- 
posed the doctrine of the Allmacht of natural selection; that 


Weismann’s 
theories, 


132 DARWINISM TO-DAY. 


is, that natural selection alone is capable of explaining all the 
phenomena and facts of species-forming and descent. At 
the same time he developed and announced the theory of the 
continuity of the germ-plasm, which, in a word, is the 
theory of an absolute separation of the germ-plasm from 
the soma-plasm and consequently the thorough independ- 
ence of this germ-plasm from all influence and control of 
the soma-plasm, 7. e., all that part of the body other than 
the germ cells. This carried with it the assumption that 
all the phenomena of heredity and variation depended solely 
on the germ-plasm and that the germ-plasm of any individual 
is derived, unmodified by any somatic influences, directly 
from the germ-plasm of its ancestors. This assumption in 
turn led to the logical but startling conclusion that all the 
capacity or possibility of variation for all time was present 
in that primitive ancestral germ-plasm from which the germ- 
plasm of all many-celled animals has been derived. But such 
a nearly infinite capacity for furnishing variations demanded 
the postulation of an equally nearly infinite capacity for ac- 
tual physical or structural complexity on the part of the germ- 
plasm itself, for biologists insist on a physical mechanism for 
all the physiological phenomena they find in life. So Weis- 
mann assumed an interesting but invisible and apparently 
non-testable composition of germ-plasm out of life-units, 


» called biophors, grouped into particles of a second order called 


determinants. The biophors are taken to be much larger 
and more complex units than chemical atoms, or even than 
molecules. They are groups of several to many molecules, 
each biophor, however, still ultra-microscopic, and represent- 
ing a single characteristic of cell-life. Each biophor is as- 
sumed to possess the essential attributes of living substance, 
viz., the capacity to assimilate food, to grow, and to repro- 
duce itself. The groups of biophors called determinants 
are larger, of course, but yet invisible to our best micro- 
scopes, and each represents all the characteristics which a 


DARWINISM DEFENDED. 133 


cell of any particular single kind has. Thus one kind of 
determinant represents all the attributes of the red blood 
corpuscles, another of the nerve-ganglion cells, another of a 
certain type of epithelial cells, and so on. Each determinant 
has also the power of assimilating food, growing and re- 
producing itself by division. Now the possibility of repre- 
senting in the germ-plasm the nearly infinite capacity to 
vary characteristic of this plasm has for its physical or 
mechanical basis the minute size of the biophors and deter- 
minants coupled with the inconceivably many combinations 
of different kinds of biophors possible in the make-up of the 
determinants which are, as already said, the actual structural 
representatives of, or better, controllers or producers of, 
the various kinds of body tissue and organs. 

These three general assumptions of Weismann,’ namely, 
(1) the composition of germ-plasm out of ultimate life-units 
called biophors (grouped into determinants) which deter- 
mine all the physical characteristics of the individuals into 
which the germ-plasm develops; (2) the isolation (from the 
soma) and the continuity (from generation to generation, 
from beginning to end) of the germ-plasm; and (3) the 
Allmacht of natural selection, which involves the discarding 
of all other factors of modification and species-forming than 
the natural selection of the slight fluctuating congenital 
variations produced (in an unknown manner) by infinitesi- ° 
mal changes in the determinants of the germ-plasm—these 
three fundamental and important Weismannian assumptions, 
accepted more or less nearly completely by Wallace and a 

ale number of other English biologists, and by a 
ism and Neo- few naturalists of Europe and America, con- 
Tamarckism, stitute the essential position of what is called 
neo-Darwinism. This neo-Darwinism immediately found 
many capable antagonists, and as most of the antago- 
nists were believers in some parts of the general theory 
of adaptation and species-forming first proposed by 


134 DARWINISM TO-DAY. 


Lamarck, their position came to be known as_neo- 
Lamarckism. Herbert Spencer in England, Packard, 
Osborn, and others in America, and Eimer in Ger- 
many were prominent exponents of the anti-Weisman- 
nian views. The debate was spirited, and engaged many 
biological writers, and interested the general reading 
public in the larger problems of biology more than it 
has been interested at any other time since the great struggle 
immediately following the publication of Darwin’s “Origin 
of Species.” The best known part of the general debate 
was that carried on directly by Weismann and Spencer in 
the Contemporary Review (1893 and 1894). 
The general result of the struggle between neo-Darwin- 
ism and neo-Lamarckism can be fairly stated to be, that 
Weismann’s assault on the theory of the in- 
eee sneha heritance of acquired characters was in general 
successful ; while, on the other hand, the assault 
of the anti-Weismannians on the assumptions of the isola- 
tion and continuity of the germ-plasm and of the Allmacht 
of natural selection forced from Weismann and his follow- 
ers, one by one and slowly, such radical concessions as to 
make the latter doctrine utterly untenable, and to rob the 
other of most of its significance in the consideration of modi- 
fication and species-forming. The assumption of the com- 
position of germ-plasm out of biophors and determinants 
is of course merely an interesting speculation, or tentative 
hypothesis, which, because it is untestable by scientific ob- 
servation or experiment, cannot be debated to any particular 
advantage. Weismann himself, in 1895, definitely conced- 
ing that natural selection is radically weak at its base, being 
incapable of explaining the beginnings of useful variations 
and the development (which actually occurs) of indifferent 
ones, proposed a new and radically un-Darwinian theory 
under the name of Germinal Selection. This theory (ex- 
plained in chapter viii of this book) although including the 


i» a 


DARWINISM DEFENDED. 135 


word selection in its name is fundamentally different from 
natural selection in the Darwinian sense, and is indeed 
an admission of the existence of variations maintained (not 
by means of natural selection) along definite lines, result- 
ing in a real orthogenesis. It attempts to offer a causo- 
mechanical explanation of such un-Darwinian development. 
By the theory of germinal selection, which is based abso- 
lutely on the assumption that the plasm is composed of 
biophors and determinants or at least of physical life units 
of similar type and function, Weismann hopes to strengthen 
four weak places in the general position of neo-Darwinism. 
The theory explains (1) how in Panmixia (another Weis- 
mannian contribution to neo-Darwinism, for account of 
which see chapter viii) the degeneration of useless organs 
is brought about, (2) how it is that for the continued 
development of any certain complex adaptation exactly the 
right variations shall appear at the needed time, (3) how co- 
adaptation comes to exist, and finally (4) how variations 
may come to be developed along fixed lines or in definite 
directions without the aid of personal selection. Whether 
the theory of germinal selection explains these four things 
or not, what is to us for the moment the chief interest of the 
theory is that it is put forward by Weismann, who is dis- 
tinctly the foremost neo-Darwinian, to explain just these 
things. For that makes of these things concessions that the 
neo-Darwinians, the ultra-selectionists, feel forced to offer. 
It should be noted, however, that perhaps Weismann does 
not speak for all ultra-selectionists, for example, Lloyd 
Morgan, Ray Lankester, and other English * Darwinians. 
Certainly his theory of germinal selection is accepted by 
few of them. 

On the whole, however, I think I speak perfectly fairly 
in saying that the believers and defenders of the natural 
selection theory to-day admit in large measure the valid- 
ity of those criticisms which are directed at the inca- 


err aed 
5 


136 DARWINISM TO-DAY. 


pacity of Darwinism, in its long familiar form, to account 
for the development of variations and modifications up 
to the advantageous or disadvantageous stage. They admit 
also the actual existence, and in abundant measure, of 
species differences which are of indifferent character, that is, 
of no especial utility, and make the consequent admission 
that such species ditferences cannot for the most part be 
explained by natural selection. And they also concede, or 
at least most of them, including Weismann, do, the force 
of the criticism that the assumption of the occurrence of the 
right variations at the right time is a necessity for the 
development by selection of many if not most specialisations 
of qualitative and of coadaptive character, which assump- 
tion in turn demands an explanation of causes anterior to 
selection. 

And finally most selectionists concede that selection can- 


‘not make new species by relying on the extremes of series 


of fluctuating or Darwinian variations because of the 
inevitable extinguishing or swamping of these extreme 
variations by inter-breeding with the far more abundant 
average or modal individuals of the species. Hence all 
those objections recorded in the chapters on “Darwin- 
ism Attacked” which have to do solely with this inca- 
pacity of natural selection to make use of variations too 
small or too few or purely fortuitous, or with the incapacity 
of selection to explain hosts of indifferent, non-adaptive 
species differences which actually exist, and hence with the 
certainty of its not being the only factor, if indeed a prin- 
cipal factor, in the formation of species, need not be re- 
discussed, at least to any length, in this chapter. We may 
also largely neglect those objections which are directed 
against the purely hypothetical assumptions and the extreme 
positions of the neo-Darwinians. Many of these assump- 
tions, such as that of the absolute isolation and independence 
from the soma of the germ-plasm, are not a part of Dar- 


DARWINISM DEFENDED. | 137 


winism proper, and the extreme position of the believers in 
the Allmacht of selection was certainly never taken by Dar- 
win himself. In fact, most of neo-Darwinism has been 
deserted by its one-time followers, and most conspicuously 
and perhaps most radically by Weismann himself. 

Thus, with these two categories of objections listed in 
the “Darwinism Attacked” chapter put to one side, for the 
moment at least, by admitting the validity of one category 
and showing the inapplicability of the other as regards its 

relation to true Darwinism, we have left to us 

The objections to consider those remaining objections which 
needing answer. : 7 

are made (1) against the capability of selec- 
tion’s making any use at all of the familiar and always 
occurring fluctuating variations called Darwinian, (2) 
against its capacity to explain coadaptive and highly com- 
plex adaptations, especially those which seem as if they 
could be of advantage to the organism only in fully 
developed or specialised state, (3) against its inability to 
account for overdeveloped specialisations, (4) against the 
possibility of selection’s explaining qualitative differences in 
species, and many-branched descent (quantitative differ- 
ences and linear descent seeming to be the only kinds pos- 
sible to it), (5) against its capacity to explain complete 
or extreme structural degeneration of useless organs and 
parts, (6) against the reality and extreme rigour of the 
struggle for existence and personal selection (an essential 
foundation of the selection theory), (7) against the sexual 
selection theory, particularly in its capacity as a supporting 
prop of the natural selection theory, (8) against the reliance 
by the selectionists on the homology or analogy which they 
hold to exist between natural selection and artificial selec- 
tion, and finally to consider those curiously positive and 
definite declarations of such radical anti-Darwinians as 
Wolff, Korschinsky, and others that natural selection is a 
vagary, having no claims to existence either on a basis of 


138 DARWINISM TO-DAY. 


observation or logical reasoning, or that if it exists its whole 
influence is directly inimical to changes and evolution rather 
than of a nature to produce and foster them. The most 
comprehensive, fairest, and most effective recent attempt 
to gather together and meet seriatim the objections and 
criticisms of Darwinism is (as already stated in the chapter 
on “Darwinism Attacked”) that of Ludwig Plate,’ and I 
have therefore given considerable space in this chapter to 
direct quotations from the answers and discussions of this 
modern Darwinian champion. 

The objection made that natural selection can make no use 
at all of the small fluctuating Darwinian variations is really 

ee era a wider application of the really valid objection 


objection that that such variations cannot, or can only rarely, 
fluctuating vari- 
ations are too 


selective value. 


cannot serve as handles for selection. As a matter of 
fact, however, many adaptive modifications are purely quan- 
titative, not necessarily involving any qualitative change 
at all. Increase in general size, or in any one dimension 
of an organ or part, meaning often an increase of strength 
on the part of the animal, in the capacity for aggres- 
sion or defence, in swiftness, in flight, running or swim- 
ming, in reaching or digging or climbing or leaping— 
such an adaptive modification might well be brought about 
by selection of even very inconsiderable enlargements or 
strengthenings of one or more organs or parts. Wherever 
the modification is in a directly linear path, and an advantage 
is possible through even slight advances or regressions along 
this line, natural selection will find in the Darwinian varia- 
tions a means of fostering and perfecting this modification. 
There are just two requirements necessary for the Darwin- 
lan variations to meet in order to serve as handles for 
natural selection: they must be variations actually suffi- 


offer material for the production by selection of | 
slight tobeof new organs and that for many adaptations) 
they are too slight to be of use and hence 


eee ee > 


DARWINISM DEFENDED. 139 


ciently useful and advantageous to turn the scale in the intra- 
or inter-specific struggle for existence in favour of the 
individuals possessing them, and they must occur in suffi- 
ciently many individuals to avoid being swamped or 
extinguished by cross-breeding: that is, they must be useful 
enough to be selected and numerous enough to perpetuate 
themselves. Do Darwinian variations ever meet these re- 
quirements? Unfortunately our proof is rather indirect: 
observation reveals their abundance, but does not actually 
- show their utility.” To answer the question our judgment 
and reason, based on our knowledge and experience of the 
existing conditions of animal and plant life, will have to 
be trusted for answer. How real is the rigour; how keen 
the struggle ; how crowded the square yard or square mile; 
how great or how little must be the differences in a part to 
give a life-or-death decision in the competition? Each 
naturalist must answer this for himself, and the layman 
must take the general consensus of opinion of the natural- 
ists, if there is one, for his answer. 
The objection to the linear and quantitative character of 
the Darwinian variations has been recently especially urged 
by de Vries in connection with his exposition 
areas of the theory of species-forming by mutations. 
cerning the The selection theory reckons with linear hence 
linear and quan- : Big Sas 
titative charac- Strictly quantitative variations, says he, and yet 
ean enee is presumed to create new forms for which in 
reality qualitative variations are necessary as 
a basis, so that in fact selection can only increase or 


diminish, add to or subtract from characters already in | 


existence and cannot create anything new, this appear- 
ance of new characteristics being, however, precisely the 
principal peculiarity of new species, taken by and large. This 
position of de Vries has been discussed by Plate‘ as follows: 

“T call attention in advance to the fact that de Vries 
understands by ‘linear variations’ what are more usually 


——— 


140 DARWINISM TO-DAY. 


known as individual, fluctuating or continuous variations. 
He has chosen this name because the single characteristic 
can change toward but two directions; that is, toward the 
plus, or toward the minus direction. In contrast to this 
kind of variation stand the sudden and discontinuous leap- 
like changes or mutations which have been for the first 
time carefully investigated by the praiseworthy labour of 
de Vries, hitherto having been familiar indeed under the 
names ‘single variations’ or ‘sports,’ but little studied. Con- 
cerning these linear variations de Vries writes: “The statis- - 
tical method of the study of variation has now been so 
generally followed as to make its principles familiar without 
further discussion, and they may be considered as accepted. 
The chief principle indicated by the use of the frequency 
curves is that the characteristics vary in but two directions, 
that is toward plus or toward minus. The old vague con- 
ception of an all-sided variation of the single characters 
has disappeared of its own self.’ 

“As highly as I appreciate the great service of de Vries 
in relation to our knowledge of the suddenly appearing 
changes, heritable in high degree, I must nevertheless op- 
pose him in his conclusions touching the selection theory. 
In the first place this theory does not reckon alone with 
linear variations, but also with mutations, if they appear, 
for it takes the changes as given material without troubling 
itself about differences in their mode of origin. In the 
second place it is not correct that a character cannot so 
change itself through simple addition or reduction that it 
may not be, in the customary classificatory limits, looked on 
as a new character. A smooth leaf, a leaf with few small 
hairs, and one with a thick wool show only linear variations, 
but in spite of that they may very well serve as character- 
istic of different species. Nearly related butterflies—recall 
the Vanessas and Lycenas—often show the same funda- 
mental characters of pattern and form, so that they are dis- 


DARWINISM DEFENDED. 141 


tinguished only by plus or minus variations. Indeed one 
may consider the whole endless manifoldness of organic 
combinations as only representing greater or lesser num- 
bers of atoms of the same few elements which are bound to- 
gether in one molecule. In the third place the statistical 
studies of variation have not shattered in any respect the 
conception of an all-sided variation of the single characters, 
but indeed on the contrary have rather shown that all the 
parts and attributes of organisms that are accessible to 
observation appear to us more or less different in different 
individuals. This all-sided variability has nothing to do 
with the statement that each single variable element can 
vary always only toward plus or toward minus. Blue 
flower petals can appear more or less blue and at the same 
time reveal their indeterminate, fortuitous, or all-sided 
variability in differences of form, hairiness, thickness, 
structure, etc. The same indeterminateness which de Vries 
claims for his mutations is characteristic also of linear 
variations.” 

Tayler,’ a Darwinian defender, has discussed this objec- 
tion as follows: “This objection appears to me to be one of 
the most weighty of all the objections which have been raised 
to the selectional hypothesis, and it is further an extremely 
difficult objection to satisfactorily reply to; first, because it is 
almost impossible to say in what form of organism the earli- 
est variations appeared, and without this no judgment on the 
value of any small variation can be of use; secondly, it is 
equally essential to know the kind of environment which 
such an organism was living in; and lastly, if we were 
fully acquainted with the character of the organism and its 
environment it would still be difficult to form any adequate 
opinion on the value of such a variation, owing to the fact 
that this apparently simple organism would differ so widely 
from our own functional activity and life that any conclu- 
sions formed on comparative methods of testing its powers, 


142 DARWINISM TO-DAY. 


etc., would be extremely likely to be fallacious. If, however, 
we keep in mind the facts that (1) the whole and not merely 
a part of the organism is selected, and that, therefore, 
each variation does not require to be of the same value as if 
selection depended on it alone; (2) specialisations are 
largely quantitative, between man at one extreme of de- 
velopment and a simple unicellular organism at the other, 
the difference, though very great, is mainly due to the fact 
that man is a huge multicellular colony ; this difficulty will be 
much simplified. To estimate the quantitative difference it is 
necessary to endeavour to determine the specialisation of an 
individual cell in one of those collective specialisations or 
organs: the difference between a cell in, for instance, the 
cerebral cortex of man and the character of an ameeba is no 
doubt great, but the amceba reacts to stimuli, though in a 
less specialised form, just as the cortex cell does; in the same 
way tne reaction to light in the mammalian eye is not a new 
development—it has its beginnings in the preference for 
light or darkness shown by many unicellular organisms. 
These two points, that selection is organismal and that 
specialisations are as, or more, largely quantitative than 
qualitative, weaken if they do not abolish all those diffi- 
culties to natural selection that are founded on this objec- 
tion, and it is further necessary to recollect that no specialisa- 
tion has yet been found which has not a primitive counter-. 
part in the earliest known forms of life.” 
With regard to the objection that because natural selec- 
tion working with fluctuating Darwinian variations is 
working only with linear or quantitative varia- 
idee es tions and therefore cannot produce many- 
selection cannot branched descent (which is certainly the kind 
Sechiie jerent Of descent that exists) but only straight-line or 
and discontinuity mono-typic descent, it is obvious that the Dar- 
adit winian answer to this is partly that of the 
answer to the objection discussed in the last paragraph. In 


DARWINISM DEFENDED. _ ag 


addition it is partly that of the answer to the objection to 
be mentioned in the next sentence. This related objection 
is that while natural selection may produce continuous 
gradatory adaptive change or evolution it cannot produce 
discontinuity in the series, 7. e., cannot produce separated 
distinct species. This objection receives an answer which 
is of the nature of an admission that natural selection wholly 
unaided really cannot differentiate species. It must call to 
its aid some isolation or segregation factor, and as isolation 
is certainly most commonly effected through migration and 
geographic means, it is usually this factor of geographic 
isolation that natural selection must be accompanied by to 
form new species. As Plate says: “Any particular phase 
of the struggle for existence extinguishes all those indi- 
viduals which do not possess certain absolutely necessary 
characteristics. By this means there is produced a common 
type. And only when some means of isolation is added can 
the splitting of the species into two or more forms result. 
Natural selection can only transform a species gradually 
and develop it in a continuous forthright line; alone it cannot 
produce a divergent, tree-like evolution. This results from 
geographic, biologic, or sexual isolation, which is in most 
cases a form of the extensive manner of working of the 
struggle for existence. But selection can aid in the differ- 
entiation of a species into two or more forms, as the following 
examples show. When all average or median-sized in- 
dividuals of a species are killed out there remain only the 
smallest and the largest, by which we may assume that the 
first are saved because they can most readily conceal them- 
selves, while the latter find in their great size a sufficient 
protection. On the ground of this difference in size perhaps 
both forms will be inclined to keep apart from each other 
and if to this is added a somewhat differing habit of life, 
two races can arise which in course of time will become 
distinct species. From a butterfly kind of very variable 


144 DARWINISM TO-DAY. 


colour-tone all brown individuals might disappear for some 
special reason while both the lighter and darker individuals 
might persist. Now if in consequence of this contrast a 
racial feeling should develop between the light individuals 
on the one hand and the dark ones on the other, the differ- 
entiation into two species is already begun. Ifa snail species 
living in fresh water is so harassed that it can only maintain 
itself when its individuals move either into the region be- 
tween tide-lines or into the deeper water, this would lead to 
morphological differentiation, as we can indeed actually note 
in the case of the chitons.”’ 
The objection that the existence of coadaptive and highly 
complex adaptations, especially those which seem as if they 
could be of no possible advantage to their pos- 
Seo Be sessors except in their present fully developed 
cerning complex OF specialised state, 1s one which unfortunately 
Tea cannot be definitely refuted or proved by ever 
so much ingenious explaining or discussion in 
the face of the lack of what we certainly do not now 
possess, namely, direct observational or experimental evi- 
dence. For such specialisations as elaborate mimickry, or 
the electric organ of the torpedo, etc., which are of appa- 
rent advantage only in perfected state, the selectionist is 
forced to admit that the objector has apparently a good case, 
but for the gradual specialisation of many highly complex 
structures and specialisations through the long-continued 
selection of slight advantageous variations, Darwin and his 
followers have offered ingenious and plausible explanations. 
For the case of so complex and coadaptive a specialisation as 
the eye and its function in the vertebrates or in the insects 
and crustaceans, the possible evolution, by slight additions 
and modifications, from simple pigment fleck to the present 
marvellous visual organ, a logically irrefutable Darwinian 
argument can be made out on the basis of the real and 
constant utility and advantage of even very slight steps 


a ie 


DARWINISM DEFENDED. | 145 


forward. And so with many other complex specialisations, 
although in almost all these cases it is necessary, as Darwin 
says, to let the reason conquer the imagination. That is, the 
reasoned explanation explains, although one recoils con- 
stantly before the almost inconceivable actuality of the 
phenomenon. 

Plate has recognised this objection as one of the really 
weighty ones and has given much attention to its considera- 
tion. His conclusion is that it is necessary to rely to a 
greater or less extent on the Lamarckian factor of the 
inheritance of somatogenic characters acquired in the lif¢ 
time of the individual through the effects of use, or disuse, 
or other functional stimuli. This is, of course, direct aban- 
donment of the position maintained by such strict selection- 
ists as Weismann and Wallace, although Weismann himself, 
in order to answer the objection without having recourse 
to reliance on Lamarckian factors, introduces his new 
theory or hypothesis of germinal selection to aid natural 
selection in the difficulty presented by the objection. Lloyd 
Morgan’s” answer to this objection consists chiefly of the 
formulation of the theory of orthoplasy (explained in chapter 


vili of this book). It is, briefly, that every organism, from) | 


its somatic and germinal aspects, exhibits two tendencies 
of variability. The somatic variability is determined largely 
or at least modified largely by environmental influences ; 
therefore those organisms whose somatic tendency is pre- 
dominantly plastic will survive under altered conditions of 
environment, where those organisms of a less easily mod- 
ifiable tendency will be eliminated. Now if somatic changes 
rarely or never become germinal, 1.e., are inherited, the mod- 
ifications of the parental organisms cannot be transmitted 
to their offspring, but those offspring that happen to be 
endowed with germinal variations in the same direction 
as the acquired but not transmitted modifications would 
start their life with a predisposition favourable to their 


\| 
1} 
ij 
i] 


146° DARWINISM TO-DAY. 


environment and therefore favourable to more complete 
modification of the somatic side of the organism; this tend- 
ency being accumulative under constant conditions, coinci- 
dent variability would arise by the process of selective 
elimination and preservation, without the need of the 
assumption of use-inheritance, which assumption facts 
appear to negative. 
Against the criticism that natural selection cannot explain 
over-developments of specialisation, that is, the carrying 
unnecessarily far of advantageous structural 
Answer to the . : 
objection con. 22d functional development, as illustrated by 
cerningover- the great antlers of stags and moose, the micro- 
specialisation. ; ; ' : ais 
scopic fidelity of simulation and mimicry, and 
the nearly identical equivalence of the right and left halves 
of bilaterally symmetrical animals, the selectionist has little 
to offer except the always pertinent questions: Are we sure 
that the case in point is one of over-development, of unnec- 
essary specialisation? And although the palzo-zoologists 
may be pretty emphatic in their declarations that the ex- 
tinction of the Irish stag and of the unwieldy cretaceous 
reptiles was directly due to over-specialisation, they cannot 
prove it. And there you are, says the Darwinist. 
The difficulty that natural selection has with structural 
degeneration is admittedly a real one. The strict Darwinian 
answer has to be that retrogression is produced 
Consideration _. ; : 
of the objection Cither by reversed selection, that is, that when 
concerning de- by a change in the life habits or external condi- 
pont cup tions a certain function or organ becomes inju- 
rious, as in the case of insects on small exposed islands 
where the wind might carry the flying ones off into the 
ocean, selection, on the basis of advantage, would tend to 
preserve the ones most poorly equipped for flight; or it 
has to be that when the function of an organ is, because of 
change in habit or conditions, once neglected or discon- 
tinued, that is, the organ is no longer used, any slight varia- 


DARWINISM DEFENDED. 147 


tion toward reduction of the organ would be of advantage 
because of the saving in food which would be effected! But 
this is simply carrying the logic of the principle of advan- 
tage to an illogical extreme, an extreme impossible to accept. 
So Weismann devised the ingenious explanation of pan- 
mixia or cessation of selection to account for degeneration. 
That is, a rigid and persistent selective activity is as neces- 
sary to maintain a specialisation as it was to produce it. 
But even Weismann has found this explanation inadequate 
and has, therefore, found a final and sufficient explanation 
in his new theory of germinal selection. This last theory, a 
refinement of Roux’s theory of the battle of the parts, is 
ingenious, suggestive, and thoroughly interesting, but un- 
fortunately it is founded on certain assumptions concerning 
the ultimate make-up of the germ-plasm and the behaviour 
of the unit parts of it, the truth of which simply cannot be 
tested. A strictly neo-Darwinian answer, that is, one based 
solely. on selection, is therefore hard to give. Plate,’’ after 
an effective adverse criticism of the influence of the Weis- 
mannian panmixia as an explanation of the structural reduc- 
tion or atrophy of parts, concludes that such reduced or 
rudimentary organs are to be explained “through the 
inherited effects of disuse, the inherited effects of the influ- 
ences of external factors, the inherited effects of the influence 
of economy in nutrition, and, in a few cases, through re- 
versed selection. The first three principles are cnly admissi- 
ble under the assumption of the actuality of the inheritance 
of individually acquired characters, and the fourth principle 
has only a very subordinate importance.” This is equivalent 
to saying that the strict selectionist has no sufficient answer 
to the objection under present consideration. One seems 
forced to rely on Lamarckian factors for anything like a 
satisfactory explanation of actual structural reduction of 
useless organs. Tayler,’’ however, offers an explanation 
for both ontogenic and phyletic degeneration, based on the 


148 DARWINISM TO-DAY. 


“known facts of nutrition.’”’ The interested reader may find 
this explanation in the appendix to this chapter. 
Doubt is expressed by some biologists of the reality and 
fierceness of the struggle for existence which is an essential 
part of the selection theory. De Vries ex- 
Answer to the : : : ; 
bbléctions ureed DEesses the belief that the intra-specific strug- 
against therig- ole, that is, the struggle and competition among 
our of selection. | |. . : 
individuals of the same species, has been much 
overrated. And a few observations ** have actually been 
made which indicate that for certain species this struggle 
is at least not rigorous enough to give to the slight Dar- 
Winian variations a determining value as to the character 
of the surviving individuals. Here again the proof for the 
Darwinian point of view is not one so much of observa- 
tion—although actual life-and-death combats between indi- 
viduals of a single species, and innumerable examples of 
the preying of one species on another are familiar—as it is 
a proof of reasoning. The fact of an over-production of 
eggs and embryos, that is, of reproduction by multiplica- 
tion, is undeniable. The lack of existing space and food 
for all individuals, if all should live the ordinary span of 
life peculiar to the species, is demonstrable by mathematics. 
The consequent conclusion of these two established premises 
is a struggle for existence. That is the sound Darwinian 
position. 
The principal answer of the Darwinians to the criticisms 
levelled at the theory of sexual selection is, that. however 
ineffective the theory is to explain many of the 
Answer to the fan A 
objections to the Phenomena it is called on to cover, it is at least 
semaine so much more reasonable and satisfying as an 
explanation of some of the phenomena, that is, 
some of the categories of secondary sexual characters, such 
as the ornamental plumes and colour-patterns of birds, the 
sound-making organs of insects, etc., than any alternative 
explanation that has been offered, that until a better expla- 


DARWINISM DEFENDED. 149 


nation be presented the theory of sexual selection should 
not be discarded. That no other explanation of many, if not 
most, of the phenomena in question has anything at all 
convincing or satisfactory about it, or has met with any 
general acceptance on the part of naturalists, is the plain 
truth. If we feel it imperative to give our adherence, with 
certain reservations, to any explanatory hypothesis of sec- 
ondary sexual characters, Darwin’s theory is the one to 
have first claim on us. As a matter of personal opinion I 
feel no necessity for any such attitude and am willing to 
look on most of the phenomena connected with the general 
problem of secondary sexual characters as quite inexplica- 
ble on the basis of our present knowledge of bionomics, 
The specific answer of Lloyd Morgan” and other Dar- 
winians to the objection that choice on the part of the 
female assumes an esthetic recognition and preference 
which it is doing violence to our knowledge of animal 
psychology to assume, should not be overlooked. This 
answer is, put summarily, that this so-called choice is one — 
of impulse, not deliberation: it is an imperative reactson to 
a sufficient stimulus: and what determines that the stimulus 
from one male shall be sufficient while that from another is 
not, is the degree of pronouncedness or effectiveness of the 
ornament, or call, or behaviour. It is a choice “which is 
determined by the emotional meaning of the conscious mean- 
ing. And it is the reiterated revival of the associated 
emotional elements which generates an impulse sufficiently 
strong to overcome her instinctive coyness and reluctance. 
It is a perceptual choice arising from impulse rather 
than an ideational choice due to motive and volition.” 
Regarding Wolff’s argument that an explanation of these 
characters is very necessary to the acceptance of the theory 
of natural selection there is little to say in rebuttal. Natural 
selection confesses itself inadequate to explain those ex- 
traordinary characters and conditions by which the males 


150 DARWINISM TO-DAY. 


of many species of mammals, birds, insects, spiders, etc., 
differ from the females. And if sexual selection does not 
explain them then some other explanation is necessary. But 
the lack of this explanation does not invalidate the general 
theory of natural selection as one of the factors in organic 
evolution and indeed one of the most important and far- 
reaching ones. 
The difficulty of a satisfactory discussion of the objection 
that natural selection rests too largely on an assumed likeness 
to artificial selection, while the differences in 
Consideration the two processes, especially in their results, are 
of the objection i 
that natural se- too radical to allow us to rest any confidence 
eae rests to on this apparent homology, is, that despite the 
assumed analogy Several thousand years through which artificial 
i Siamaaias selection has been followed and studied we 
still know too little of the real character of it, 
especially of its results. Most selectionists now admit that 
the argument for natural selection on the basis of its sim- 


_ilarity to artificial selection has been given too great promi- 


nence and relied on too strongly, but that the observed 
processes of the one do teach us much of truth about the 
unobservable processes of the other the Darwinians firmly 
maintain. As Plate says, “The great value of artificial 
selection consists in this, that it shows first, that a gradual 
cumulation of characteristics in definite directions is actually 
possible through successive selections, and second, that it 
has afforded us a rich mass of data concerning variation, 
inheritance, and the influence of changing intrinsic condi- 
tions or influences. When Darwin showed what a high 
plasticity the domestic animals possess he built for his 
theoretical explanation of descent an indubitable necessary 
foundation, for the changes which a domestic animal passes 
through in the hands of man must of necessity be able to 
be called forth in similar manner in the feral animals by 
the creative force of nature, for the domestic animals cer- 


DARWINISM DEFENDED. I51 


tainly have come from the wild ones. It is also true that 
man has made use of only natural factors, and whoever will 
compare the extraordinary creatures of the deep sea with 
even the most bizarre of our cultivated races, will see that 
the fluxing life-conditions of free nature can modify or 
reform the animal world in no less degree than the intelli- 
Sencevor man: can do-it] 1: 

“Recently de Vries,’* in his book on ‘Mutations,’ has tried 
to deny the worth of the selection principle, and although 
I fully recognise the high worth of his contribution to science 
based on such extensive series of experiments, yet I must 
oppose him in this position. In various places in the book 
he writes that nothing fixed can be produced by selection, 
and that therefore it can have no importance as a working 
factor in descent. For example, in the introduction (p. 6) 
he says: “Artificial selection never, as far as experience 
reaches, leads to the origin of new complete types.’ The 
reversion of modified domesticated races is indubitable, and 
de Vries himself has brought forward new illustrations of 
this fact which has been so long known. But convincing 
proof that natural selection cannot lead to constant forms 
cannot be deduced from these observations, because they 
refer in all cases to forms which have been highly modified 
in the course of a few years or decades, so that the pre- 
sumption lies close at hand that there has not been sufficient 
time really and lastingly to modify the original heredity 
established by centuries. Many facts indicate that the in- 


tensity of heredity depends upon the number of generations, | 
that is, upon time. Long-inherited characters are difficult/: 


‘oO peradicate » recent’ ones) :easy, We! can; therefore, not 
expect to meet such a constancy in the products of a century 
as we find in Nature. Many gradually selected races of 
doves are now almost entirely constant, that is, no longer 
revert to the primitive race when they are inter-bred. The 
way in which the reversions appear shows that the duration 


eee 


152 DARWINISM TO-DAY. 


of time plays an important role in inheritance (heredity). 
Schubeler found in his studies of the translation of the 
northern boundary of the grain culture that the characters 
newly acquired (heavier and earlier ripening seeds) per- 
sisted for several generations when the forms were replanted 
in the original [more southerly] habitat. De Vries in six 
years selected corn which had an average of 20 rows of 
kernels instead of the original 12 to 14, and held the plants 
at this height of production through five years. When he 
then planted seed from a 16-rowed ear, the average of the 
ears gathered from this planting was in the first generation 
still at 20 rows, and sank only in the next two years again 
to 14 to 16. If he had continued his selection longer he 
would have arrived at a more nearly constant form. De 
Vries himself says: ‘When the selection ceases, the selected 
characteristics drop away and in practically the same length 
of time which was necessary for the production of the new 
race, that is within a few generations.’ From this it follows 
that a domestic race produced by slow persistent selection 
through many thousands of generations would show the 
same relative constancy or fixity as natural species, the 
majority of which also must have originated slowly, for 
otherwise the appearance of new species would be often 
observed. If one wishes to be very conservative in this 
matter one may declare: in the light of our present knowl- 
edge we cannot say that artificial selection gives us any safe 
means of judging just what degree of constancy [fixity] can 
be attained by its means; but it is not fair to say that be- 
cause up to the present only a partial constancy has been 
reached through artificial selection, natural selection cannot 
have led to the production of constant species. All culti- 
vated races have been relatively quickly, some indeed very 
quickly, selected ** and, therefore, they strike back very 
quickly. This, however, need not be assumed for the slowly 
arisen products of natural selection.” 


DARWINISM DEFENDED. 153 


Tayler,’* making a general defence of the natural selection 
theory, says: “To realise how far the theory of selection is 
capable of explaining the facts of organic evo- 
Tayler’s gen- : <0 : : 
eral defense of lution, it is necessary to bear in mind the 
natural selection. Hoctulates on which the theory is founded. 

“tT, It is obvious that natural selection can only act by 
preserving or eliminating the complete organism. Selection 
must therefore be organismal. This Darwin and other 
selectionists have clearly recognised. 

“2, As the whole organism must survive, if the favoura- 
ble variation or variations aré to be preserved, it follows that 
certain minor unfavourable variations may also be pre- 
served if they happen to exist in an individual which sur- 
vives on account of its major favourable variations. And 
since no individual is completely adapted to its environment, 
it follows that there must be always a variable amount of 
residual unfavourable variability in every organism. 

“32. This residual unfavourable variability may be of con- 
siderable utility under changed conditions. 

“4. Complementary specialisation of parts, as Spencer 
has shown, is favourable to successful competition, and as it 
is the whole organism that is selected or eliminated, it fol- 
lows that any weakness of one specialised part, since it would 
disturb the balance of all, would be detrimental. The more 
complex the organism, the more specialised the structures, 
the more dependent one part will be on the others for its 
existence, hence a complementary specialising tendency will 
be favoured by selection, and therefore all struggles of one 
part of an organism with another will be reduced to a 
minimum. | 

“Tt is clear that there must be some underlying criterion 
which determines whether any given organism shall be 
selected or not, and that criterion must be the net result of 
its adaptability to its environment. One organism may con- 
ceivably survive, by its possession of a large number of small 


154 DARWINISM TO-DAY. 


favourable variations, while another may survive in virtue 
of a single valuable one, but in each case it would be the 
whole value of that organism which determined its survival. 
This fact is continually disregarded by opponents of the 
neo-Darwinian position, yet this selection of the organism 
as a whole is the fundamental postulate from which the 
theory of selection starts. Thus it is not uncommon to 
read criticisms bearing on the early development of some 
organ, in which the inadequacy of selection is supposed to 
be proved by the writer demonstrating, or believing he has 
demonstrated, the fact that the particular variation in ques- 
tion must have been too small to be by itself of selection 
value. In many cases the particular variation would, no 
doubt, if taken alone be, as the objector asserts, too unim- 
portant to be selected, but as it is the whole organism that 
is selected, it is not logical to make an artificial separation 
and study the development of one organ or structure irre- 
spective of the other organs with which it is in nature asso- 
ciated. Every organ in its evolution must be considered in 
relation to the whole of the particular organism in which 
that particular stage of development of that organ is found. 
Starting, therefore, with this fact that the net value of 
adaptability of the whole organism to its environment must 
be the basis which determines selection or elimination, it 
will follow that certain lines of development will result from 
the application of this criterion. In a series of organisms 
placed under new conditions, elimination will proceed along 
lines essential to bring about a proper adjustment to the 
new conditions. If the offspring of these adjusted organ- 
isms merely repeated in their generation the characters of 
the exterminated as well as of the surviving organisms, 
that temporary adjustment would be permanent as long as 
the conditions were unchanged. But since the offspring are 
produced ‘only by the surviving organisms, selection is con- 
tinually raised to higher and higher planes of adaptation, 


DARWINISM DEFENDED. — BES 


and, therefore, as long as conditions remain constant, the 
tendency of selection must be, as Darwin clearly saw, cumu- 
lative. He did not, however, apparently see that from this 
cumulative tendency definite variability must arise out of 
indefinite. 

“Selection in direct relation to climatic conditions is, there- 
fore, of very minor importance, while selection among the 
members of a species and all forms of inter-organismal 
selection is of infinitely more importance, since it is this 
interaction, produced by the offspring in different degrees 
inheriting the advantages of both parents (both of whom 
have survived on account of certain advantages), that leads 
to the cumulative development and never-ending struggle 
for survival. Darwin came very near to this conception of 
definite variability when he pointed out that ‘if a country 
were changing the altered conditions would tend to cause 
variation, not but what I believe most beings vary at all 
times enough for selection to act on.’ Extermination would 
expose the remainder to ‘the mutual action of a different 
set of inhabitants, which I believe to be more important to 
the life of each being than mere climate,’ * and as ‘the same 
spot will support more life if occupied by very diverse 
forms,’ it is evident that selection will favour very great 
diversity of structure. 

“Bearing in mind this cumulative action of selection it 
will follow that under constant or relatively constant con- 
ditions the struggle for successful living will become more 
and more selective in character, even if the actual number 
of inhabitants remain more or less the same as when the 
struggle first commenced. The selection of variations will 
thus tend to pass through certain more or less ill-defined, 
but nevertheless, real stages. In proportion as the struggle 
becomes intense, either from the number or from the in- 


*From Poulton’s “Charles Darwin and the Theory of Natural 
Selection” (Abstract of Darwin’s letter to Professor Asa Gray). 


a 


156 DARWINISM TO-DAY. 


creasing adaptability of the organisms, or both, certain 
major essential adaptations, which were necessary for the 
climatic and other more or less comparatively simple con- 
ditions, will be supplemented by minor auxiliary variations 
which in the earlier stages would not have appeared. And 
still later, as more and more rigorous conditions of life were 
imposed, the advantage would tend to rest with those organ- 
isms which possessed highly coordinated adaptations, since 
this would entail more rapid responsiveness to environment. 

“As evolution advances from the unspecialised to the spe- 
cialised, and higher and higher forms of life come into 
being, with increasing complexity and specialisation of parts 
entailing an increasingly delicate adjustment of those parts 
to each other’s needs, the relation of each part to the whole 
organism becomes of more and more importance, and it 
follows that selection must become more and more general- 
ised in its action. No single variation could be of service 
to any of the higher forms of life unless it was in more or 
less complete harmony with the whole tendency of the 
individual. The adjustment of parts and their mutual inter- 
dependence make it essential for adaptation that the relation 
of parts be preserved; consequently, correlated minute 
favourable variations will tend to be more and more selected 
as evolution passes from the unspecialised to the specialised 
forms of life. This response of the whole organism should 
be still more delicate in those forms of life that are con- 
tinually subjecting themselves to changed conditions; hence 
this delicacy of adjustment is far more necessary in the 
higher forms of animal life than in the more stationary plant 
organisms, and in the developing nervous system of animals 
we have just the central adjusting system that is required for 
these conditions. Wiuth evolution of type there will thus be 
an increasingly definite tendency given to organic, espe- 
cially the animal, forms of life, if the acting principle of 
evolution has been selectional. Selection is, therefore, able 


DARWINISM DEFENDED. 157 


to account for the steadily progressive tendency of life as a 
whole without calling to its aid any unknown and doubtful 
perfecting principle. 

“To summarise :—Natural selection, acting on the whole 
organism, tends to produce more and more definite tend- 
encies in all surviving forms of life, which tendencies are 
progressive and continuous in character. Variable condi- 
tions, by partially altering the line of selection, induce a 
temporary indefiniteness. And lastly, the process of selec- 
tion being itself able to be the indirect, though not the direct, 
cause of those favourable variations, which it subsequently 
selects from, is able to dispense with any subsidiary factors, 
provided it has a certain number of elementary properties 
of life which afford sufficient material to work with.” 


APPENDIX. 


* Semper, Carl, “Der Haeckelismus in der Zoologie,”’ 1876. 

In 1876, Gustav Jaeger anticipated Weismann’s later much- 
heralded theory of the continuity of the germ-plasm in his 
“Zoologische Briefen.” 

*For an excellent detailed critical account of these general, as 
well as the several accessory theories (amphimixis, polar bodies, 
etc.) of Weismann, see Romanes’s ‘““An Examination of Weismann- 
ism,” 1893. 

*It is of interest to note that the strongest defenders of neo- 
Darwinism to-day are the English naturalists. Americans mostly 
lean toward neo-Lamarckism; the Germans are divided. 

* Plate, Ludwig, “Uber die Bedeutung des Darwin’schen Selec- 
tionsprinzip und Probleme der Artbildung,” 2d ed., 1903. 

* Prof. Weldon, an English Darwinian, has recorded (Nature, 
Sept. 22, 1898) an extremely interesting and much discussed statis- 
tical and experimental study of the presumable action of natural 
selection working on slight fluctuating quantitative variations. “I 
can only attempt to discuss,’ says Prof. Weldon, “the importance 
of small variations, and the rate of organic change, in the one case 
which I happen to know. The particular case I have myself studied 
is the variation in the frontal breadth of Carcinus menas [a small 
shore-crab]. 


158 DARWINISM TO-DAY. 


“During the last six years my friend, Mr. Herbert Thompson, and 
I have studied in some detail the state of this character in the 

Weldon’s ex- small shore-crabs which swarm on the beach below 
periments on the laboratory of the Marine Biological Association, 
Carcinus. at Plymouth. 

“T will show you that in those crabs small changes in the size of 
the frontal breadth do, under certain circumstances, affect the death- 
rate, and that the mean frontal breadth among this race of crabs is, 
in fact, changing at a rate sufficiently rapid for all the require- 
ments of a theory of evolution. 

“In Table IV [omitted], you see three determinations of the 
mean frontal breadth of these crabs, expressed in terms of the 
carapace-length, taken as 1,000. You see that the mean breadth 
varies very rapidly with the length of the crab, so that it was neces- 
sary to determine it separately in small groups of crabs, such that 
the length of no two crabs in a group differed by more than a 
fifth of a millimetre. The first column of the table shows you the 
mean frontal breadth of twenty-five such groups, between Io and 15 
millimetres long, collected in 1893. These crabs were measured by 
Mr. Thompson. The second column shows you the mean frontal 
breadth in twenty-five similar groups of crabs, collected in 1895, and 
also measured by Mr. Thompson. You see that in every case the 
mean breadth in a group of crabs collected in 1895 is less than it 
was in crabs of the same size collected in 1893. The third column 
contains the result, so far as it is yet obtained, of my own measure- 
ment of crabs collected this year. It is very incomplete, because 
the 1895 crabs were collected in August and September, and I was 
anxious to compare them with crabs collected this year at the same 
season, so that there has not yet been time to measure the whole 
series. The measurements are sufficient, however, to show that 
the same kind of change has taken place during the last three 
years as that observed by Mr. Thompson in the interval between 
1893 and 1895. Making every allowance for the smallness of the 
numbers so far measured this year, there is no doubt whatever that 
the mean frontal breadth of crabs from this piece of shore is 
considerably less now then it was in 1895 among crabs of the 
same size.* 

“These results all relate to male crabs. The change in female 


*T shall, of course, consider it my duty to justify this statement 
by more extensive measurement as soon as possible. In the mean- 
time I may say that I have measured other small groups of crabs, 
male and female, from the same place, at different seasons of the 
ee 1896-98, and the results agree with those recorded in the 
table. 


DARWINISM DEFENDED. 159 


crabs during this time has been less than the change in male crabs, 
but it is, so far as my measurements at present permit me to speak,. 
going on in the same direction as the change in male crabs. 

“T think there can be no doubt, therefore, that the frontal breadth. 
of these crabs is diminishing year by year at a rate which is very 
rapid, compared with the rate at which animal evolution is com- 
monly supposed to progress. 

“T will ask your patience for a little while longer, that I may 
tell you why I feel confident that this change is due to a selective 
destruction, caused by certain rapidly changing conditions of 
Plymouth Sound. 

“On either side of Plymouth itself a considerable estuary opens. 
into the Sound, and each of these estuaries brings down water 
from the high granite moorlands, where there are rich deposits of 
china clay. Those of you who know Dartmoor will remember that 
in rainy weather a great deal of china clay is washed into the 
brooks and rivers, so that the water frequently looks white and 
opaque, like milk. Much of this finely divided china clay is carried 
down to the sea; and one effect of the breakwater has been to 
increase the quantity of this fine silt which settles in the Sound 
itself, instead of being swept out by the scour of the tide and the 
waves of severe storms. 

“So that the quantity of fine mud on the shores and on the bot- 
tom of the Sound is greater than it used to be, and is constantly 
increasing. _ 

“But this is not all. During the forty or fifty years which have: 
gone by since the breakwater was completed, the towns on the 
shores have largely increased their population; the great dockyard 
at Devonport has increased in size and activity; and the ships. 
which visit the Sound are larger and more numerous than they 
were. Now the sewage and other refuse from these great and 
growing towns and dockyards, and from all these ships, is thrown 
into the Sound; so that while it is more difficult than it used to be 
for fine silt to be washed out of the Sound, the quantity thrown into 
it is much greater than it was, and is becoming greater every day. 

“Tt is well known that these changes in the physical conditions. 
of the Sound have been accompanied by the disappearance of ani- 
mals which used to live in it, but which are now found only outside 
the area affected by the breakwater. 

“These considerations induced me to try the experiment of keeping 
crabs in water containing fine mud in suspension, in order to see 
whether a selective destruction occurred under these circumstances 
or not. For this purpose, crabs were collected and placed in a large 
vessel of sea-water, in which a considerable quantity of very fine: 


160 DARWINISM TO-DAY. 


china clay was suspended. The clay was prevented from settling 
by a slowly moving automatic agitator; and the crabs were kept 
under these conditions for various periods of time. At the end 
of each experiment the dead were separated from the living, and 
both were measured. 

“In every case in which this experiment was performed with 
china clay as fine as that brought down by the rivers, or nearly so, 
the crabs which died were on the whole distinctly broader than 
the crabs which lived through the experiment, so that a crab’s 
chance of survival could be measured by its frontal breadth. 

“When the experiment was performed with coarser clay than 
this, the death-rate was smaller, and was not selective. 

“T will rapidly show you the results of one or two experiments. 
The diagram [omitted] shows the distribution of frontal breadths, 
about the average proper to their length, in 248 male crabs treated 
in one experiment. Of these crabs, 154 died during the experiment, 
and 94 survived. The distribution of frontal breadths in the sur- 
vivors is shown by the lower curve in the diagram, and you see 
that the mean of the survivors is clearly below the mean of the 
original series, the mean of the dead being above the original mean. 

“Two other cases, which are only examples of a series in my 
possession, show precisely the same thing. 

“These experiments seemed to me to show that very finely divided 
china clay does kill crabs in such a way that those in which the 
frontal breadth is greatest die first, those in which it is less live 
longer. The destruction is selective, and tends to lower the mean 
frontal breadth of the crabs subjected to its action. It seemed to 
me that the finer the particles used in the experiments, that is to 
say, the more nearly they approached the fineness of the actual silt 
on the beach, the more selective their action was. 

“I, therefore, went down to the beach, where the crabs live, and 
looked at the silt there. This beach is made of moderately small 
pieces of mountain limestone, which are angular and little worn 
by water. The pieces of limestone are covered at low tide with 
a thin layer of very fine mud, which is much finer than the china 
clay I had used in my experiments, and remains suspended in 
still water for some time. Under these stones the crabs live, and 
the least disturbance of these stones raises a cloud of very fine 
mud in the pools of water under them. By washing the stones of 
the beach in a bucket of sea-water, I collected a quantity of this 
very fine mud, and used it in a fresh series of experiments, precisely 
as I had before used china clay, and I obtained the same result. 
The mean frontal breadth of the survivors was always smaller 
than the mean frontal breadth of the dead. 


DARWINISM DEFENDED. 161 


“T think, therefore, that Mr. Thompson’s work, and my own, 
have demonstrated two facts about these crabs; the first is that 
their mean frontal breadth is diminishing year by year at a measur- 
able rate, which is more rapid in males than in females; the second 
is that this diminution in the frontal breadth occurs in the presence 
of a material, namely, fine mud, which is increasing in amount, 
and which can be shown experimentally to destroy broad-fronted 
crabs at a greater rate than crabs with narrower frontal margins. 

“T see no shadow of reason for refusing to believe that the action 
of mud upon the beach is the same as that in an experimental 
aquarium; and if we believe this, I see no escape from the con- 
clusion that we have here a case of Natural Selection acting with 
great rapidity, because of the rapidity with which the conditions 
of life are changing.” 

These observations and conclusions of Professor Weldon have 
been the subject of much discussion. The adverse criticism has, on 
the whole, seemed to be successful in discrediting the case as an 
example of any such clear-cut action of natural selection, as Weldon 
seems to hold it to be. J. T. Cunningham (Natural Science, Vol. 
XIV, pp. 38-45, 1809) concludes, after a critical analysis of the 
work, that ‘““Weldon’s observations may be completely explained by 
variations in the amount or rate of growth. The difference in 
different years would be at once explained if the amount of change 
in frontal breadth was constant for each moult, while the amount 
of growth was variable. The fact is, that in 1893 crabs of a given 
frontal breadth were larger than in I895 and 1898; and I have 
shown that the summer of 1893 was exceptionally fine and warm. 
Either the warmth alone, or warmth and food together, very prob- 
ably made the crabs grow more in that year for the same number 
of moults. On this view the broad-fronted crabs died in the expe- 
timents with clay and mud because they were younger and weaker. 
In the same way the crabs that moulted in the bottles possibly 
grew more than those in the sea, because they were kept in warmer 
water and supplied with more food. Therefore they were, after 
the moult, larger than those in the sea of the same relative frontal 
breadth. 

“The change described is not, if terms are used correctly, a change 
in the character of the species, but merely a change in the rate of 
development. The variations investigated are not individual differ- 
ences, since each individual in the course of its growth passes 
through each one of the variations in its own person. It has not 
been shown that the change has gone on continuously for five 
years, or that it has taken place only in waters where there is much 
mud. If tadpoles of the same size were found to have shorter tails 


162 DARWINISM TO-DAY. 


in one year than in another, few biologists would draw the con- 
clusion that the result was due to the selective destruction of those 
with the longest tails. The more probable explanation would be 
that those with the shorter tails were in a more advanced stage 
of their metamorphosis.”’ 

™ Plate, L., “Uber die Bedeutung,” etc., pp. 31-32, 1903. 

® Tayler, J. L., “The Scope of Natural Selection,” Nat. Science, 
Vol. XV, pp. 114-129, 1899. 

®* Morgan, C. Lloyd, ‘‘Factors in the Evolution of the Mammalia,” 
Nat. Science, pp. 97-101, 1892. 

° Plate, L., “Uber die Bedeutung,” etc., pp. 159-160, 1903. 

™* Tayler, J. L., ‘The Scope of Natural Selection,” Nat. Science, 
Vol. XV, pp. 114-129, 1899. I quote as follows: ‘In the development 

Tayler's ex- of the individual we see a disappearance of structures, 
planation of de- which appear to become, with advancing development, 
generation by = useless, almost parallel to the gradual disappearance of 
natural selection. -44iments, etc, in the history of the species evolution. 
And a common explanation for both of these series of phenomena 
can, I believe, be satisfactorily found in the known facts of nutrition. 
Growth of any tissue would seem to depend on three conditions, 
a stimulus of the part adequate to promote functional activity, 
a proper food supply, and efficient removal of products produced 
by that particular tissue’s activity. There is abundant evidence 
to prove that a tissue tends to degenerate if its own excretory 
products are not removed; the evil effects produced by fatigue 
products in muscle and other tissues on the activity of the tissue 
itself, prove that this factor must be of great importance where- 
ever it is found to occur. Just as the growth and development of 
bacteria are interfered with, and finally altogether checked by the 
accumulation of products of their own activity, so a tissue in the 
higher organisms has its activity impaired and its power lessened 
when for some reason diminished -elimination of its own metabolic 
products occurs. Now both in the development of the individual 
and the race we see an alteration of structure, a gradual transition 
from the less to the more specialised, and in this gradual transition 
there must be, as I endeavoured to prove in my answer to the last 
objection, an alteration in the line of functional activity of the 
parts, and that, owing to this fact, a tissue that was necessary in 
' the earlier stages became less and less so as specialisation advanced, 
the whole tendency of the specialising organism being continually 
and increasingly against the earlier, Jess specialised, stages. It will 
thus happen that every structure which is becoming useless, owing to 
its deficient specialisation, whether in the history of the race or the 
individual, will have two adverse sets of conditions to contend 


DARWINISM DEFENDED. 163 


with—one, defective elimination of its own tissue products, owing 
to its becoming increasingly removed from the growing organismal 
specialisation of food products, while secondly, for this same reason, 
its own food supply will become less and less suitable. This theory 
would apply equally to germinal and somatic development and 
atrophy of structure; there would thus, through the alteration of 
functional activity of the whole organism, be brought about elimina- 
tion of all structures not in the line of evolution; and, therefore, 
organismal selection alone, if this theory is sound, would be able 
to explain the complete disappearance of rudiments, the various 
forms of development and atrophy, without calling to its aid climatic 
inheritance, panmixia, and germinal or any other form of particular 
selection.” 

** See the account of the observations of Kellogg and Bell in the 
appendix of chap. iv. 

*® Morgan, C. Lloyd, “Animal Behaviour,” p. 269. 

** De Vries, H., “Die Mutationstheorie,” 2 vols., I90I, 1903. 

*° Plate, in a later briefer treatment (““Darwinismus kontra Muta- 
tionstheorie,” Archiv f. Rassen- und Gesellschaft-Biologie, Vol. III, 

Plate’s expla- pp. 183-200, 1906) of some of the offered objections to 
nation of charac- Natural selection refers to this matter from a slightly 
ter fixity indo- different angle. ‘‘So sehr der Zitichter danach streben 
mestic animals. muss, erblich konstante Formen zu erhalten, um der 
Muhe der bestandigen Auslese enthoben zu sein, so wenig spielt dieser 
Punkt in der freien Natur eine Rolle. Hier findet eine nie nachlas- 
sende Zuchtwahl statt, wodurch der betreffende Charakter auf einer 
gewissen Hohe erhalten und vor Riickschlag bewahrt wird. Welcher 
Grad von Konstanz nun auf diesem Wege im Laufe von Tau- 
senden von Generationen erzielt werden kann, ist eine zurzeit 
noch ungeloste Frage, die ihrer Natur nach wohl kaum mit Sicher- 
heit beantwortet werden kann. Jedoch lehrt die Tier- und Pflanzen- 
zucht, dass der Riickschlag nach dem AufhGren ~der Selektion 
um so spater und um so seltener eintritt, je langer und je intensiver 
der Ztichtungsprozess vorher betrieben worden ist. Daraus ist zu 
schliessen, dass die langandauernde Zuchtwahl, welche die Natur 
ausubt, jenen relativ hohen Grad von Erblichkeit zu erzeugen 
vermag, welcher den Spezies-Charakteren im allgemeinen zukommt, 
denn vollig konstant sind diese bekanntlich auch nicht.” 

** Tayler, J. L., “The Scope of Natural Selection,’ Nat. Science, 
Vol. XV, p. 119 ff., 1899. 


CTA EE RAGE 


DARWINISM DEFENDED (CONTINUED) : PLATE’S 
WONCIEEATORY SB PEIN GE: 


THE foregoing consideration of the answers of the Dar- 
winians to the objections urged against the effectiveness of 
the selection theory as an explanation of evolution makes 
no pretence of having included, or even referred to, all 
the arguments offered by the defenders, and it is only fair 
to note that by no means all Darwinians and neo-Darwin- 
ians agree to making the concessions listed in the early 
pareaorethe chapter.» ‘Some. réefusé: va (certain eonom on 
two of these concessions, some another or others, some 
indeed will make no admissions at all. With these last we 
are past arguing. The discussion assumes too much an “it 
is, it isn’t” character to be particularly illuminating or pro- 
gressive. But because of those who concede in considerable 
measure, and deny in some measure, the validity of those 
chief objections to the species-forming capacity of natural 
selection, the general character of the ground on which 
this last stand for the old flag is being made should at least 
be indicated. 

This half-surrendered but still not quite deserted position 
is perhaps most clearly to be seen through the smoke of 

Plate'scon- battle by fixing one’s eyes on the representative 
sideration of the Foure of Ludwig Plate, a strong Darwinian, 
objections to 
selection. but one not blinded by prejudice or with ears 
wilfully closed to the calls of reason. In his recent elaborate 
discussion * of Darwinism, so often already referred to and 
quoted from in these present chapters, he groups under the 
head of wesentliche Einwinde (important objections) the 

164 


DARWINISM DEFENDED. 165 


attacks on the species-forming capacity of natural selection, 
which are based on (1) the slightness and inutility of the 
fluctuating Darwinian variations, and (2) the improbability 
of the right variations appearing at the right time to make 
possible the development of specialisations of qualitative 
and coadaptive character. In a discussion of some length 
(pp. 32-77), mostly quite fair and unprejudiced, he brings 
out the best and strongest arguments that the faithful Dar- 
winians have to offer to reduce the force of at least, if not to 
answer satisfactorily, even for themselves, the most effective 
attacks on the capacity of selection. In very condensed form 
I present in the following paragraphs the essential points 
in these defensive arguments. 

In regard to the first objection, namely, that the very 
slight or small differences in organs and functions which 

result from the fluctuating or Darwinian varia- 

The objection .. ‘ 
to the slightness tions cannot be sufficiently advantageous or 
of Darwinian disadvantageous enough to afford “handles” 
variations, : , : 

for natural selection, that is, cannot be of life- 
and-death-determining value, Darwin devoted, in his “Origin 
of Species,’ a whole chapter of discussion and argument 
to show that in many cases even the slightest of differences 
may conceivably (it is of course a matter practically incapa- 
ble of proof by observation or experiment) be sufficient to 
turn the scale, in a rigorous competition, one way or the 
other. In many other cases such differences could not, even 
to Darwin, appear sufficient to be of a life-and-death advan- 
tage or disadvantage. But Darwin too often, Plate admits, 
confounded mere usefulness * with life-and-death-deciding 
usefulness (or non-usefulness). 

However, for many cases Plate maintains that the slight 
Darwinian variations can serve as handles for selection, 
particularly in periods of unusual rigour of competition 
or fierceness of struggle (either active or passive): ex- 
amples are, slight differences in the speed of preyed-on 


166 DARWINISM TO-DAY. 


animals when pursued by an enemy, or slight differences 
in the length of neck of the giraffe in time of scarcity of 
foliage, or slight differences in the effectiveness of the 
organs of sense at times of approaching danger, or in 
endurance. of cold, heat, hunger, dryness, etc., or in 
the clothing of hairs or feathers, the number of capil- 
laries in the skin, or richness of glandular secretion, and 
the like, in times of special stress of weather. “Dodel- 
Port * has shown that microscopically fine hairs are capable 
of keeping plant-lice away from leaves or buds, and that 
very slight differences in the specific gravity of the seeds 
of water-plants may determine whether these seeds sink to 
the bottom and consequently germinate or not. For the long 
flights of migratory birds or for birds like our house-doves 
which protect themselves from birds of prey by swift flights 
upward to great heights, every smallest amount of advan- 
tage in the pneumaticity of the bones will be of worth and 
finally of vital advantage, just as every racing bicyclist 
knows by experience that for his record-breaking at- 
tempts he must have a machine in which every part is 
made as light as possible, for the effects of weight are cumu- 
lative in course of time.” And Plate fills a couple of pages 
with other similar cases. ‘‘Whoever scrutinises the life of 
nature and of man with biologically trained eye sees over 
and over again the coming of great effects from slight 
causes. The average of accidents in factories increases in 
proportion to the age of the workers, because muscular 
strength and keenness of the sense organs decrease with 
increasing age. In each age-class the difference is but 
slight, but in spite of that it demands its sacrifice. Nageli, 
in a paper concerning the abundance of tuberculosis, showed 
that among 500 dead human bodies examined 97 per cent. 
showed traces, at least, of tuberculosis. That is, practically 
every adult human is tainted by this disease. Now how 
often must slight differences in body structure, life habits, 


DARWINISM DEFENDED. 167 


hygienic conditions, yes, even in temperament, determine 
whether there shall be healing or death? The iridescent 
colours of many male birds, butterflies, and certain parasitic 
copepods (Sappharina), are certainly of a nature to pro- 
duce a great effect on the eye, but these colour effects are 
not the result of special pigments but of microscopically 
minute structural conditions. In Africa the tsetse-fly * ex- 
tends over large regions, and only those cattle with a skin of 
a certain thickness, so that the tiny proboscis of the fly 
cannot penetrate it, can live in these regions immune from 
the fatal attacks of the pest. Many poisons work in almost 
infinitely weak dilution—a 1-200,000 solution of ricin, for 
example, is able to kill mice.” 

Plate presents a second type of answer to the objection 
by calling on certain aids or auxiliary principles by whose in- 

ites fluence a difference at first unimportantly small 
may aidslight gradually comes to be transformed into one of 
“tasers selective value, or may reach this stage sud- 
denly by means of a change in life habits. This may come 
about “through correlation,’ that is, through that unknown 
law of growth by which an indifferent organ may be so 
bound up with or related to a useful organ’® that it, the 
indifferent organ, is perfected along with the useful organ 
as this latter is developed or specialised through selection. 
All organs of an animal are intimately related to and influ- 
enced by one another: each is in relation to the other just 
as to the outer world. How close this inter-dependence is, 
is most easily appreciated by one in his own case when sick: 
a constipation causes headache, a slight diarrhoea affects the 
composition of the urine, etc. The correlation can be so 
intimate and important, as the case of the secondary sexual 
characters shows, that its origin and development depends 
directly on particular definite stages of the related organs.” 
In the case of many animals the appearance of various curi- 
ous and large modifications of legs, wings, skin, feathers, 


168 . DARWINISM TO-DAY. 


hair, etc., etc., depends on the various stages of development 
reached by the reproductive organs. Now these secondary 
organs or modifications thus produced through the influence 
of other organs may be for a while slight and indifferent 
in character, but yet safely maintained. When they reach 
a stage of utility or of positive disadvantage they will then 
be further perfected, or on the other hand be extinguished, 
by selection. 

The principle of the change of function (Functions- 
wechsel) first elaborated by Dohrn," is also called on by 

Dehene prin: Plate to play an important part in explaining 
ciple of change how an organ of considerable specialisation can 
SOE ae be shown to have been developed by selection, 
although the function it is now performing seems to be one 
that could have been useful only in a perfected state and 
hence could not have made the organ so constantly ad- 
vantageous in all the slow and gradual stages of its evolution 
as to be of selective value in its beginning stages. Dohrn’s 
principle is stated as follows: “An organ can, in its service 
of a certain definite useful function, be developed by natural 
selection to a certain stage. Simultaneously a second func- 
tion (Functionserweiterung) can have developed, due to 
some special peculiarity or condition of the position, struc- 
ture, or capacity for movement, which may have a value in 
another direction from that of the first function. Thus 
the appendages of crabs serve often special functions in rela- 
tion to respiration, copulation, and care of the eggs or 
young, while their original locomotory function may still 
be maintained or may be more and more surrendered in 
favour of the new functions.’’ Numerous other specific ex- 
amples are obvious enough to any student of biology. Now 
the new functions in many cases become the more import- 
ant so that there in time results a complete change of func- 
tion which wholly alters the physiological character of the 
organ, and in many cases it is difficult to see (if one does 


DARWINISM DEFENDED. 169. 


not know the phyletic history of the organ and the 
function) just how selection could have developed such an 
organ by slow degrees from slight beginnings. But the 
secret of the explanation, which is a perfectly consistent 
Darwinian explanation, lies in the Functionswechsel phe- 
nomenon, 

“Indifferent characters can suddenly become of selective 
value through change of environmental conditions or of 
life-habits. The cranial sutures are certainly of no vital 
importance with the reptiles and birds, but they can be of 
very great importance to the viviparous mammals as adapta- 
tions for passing the pelvis during birth. Lacerta vivipara 
has, perhaps, no advantage through its viviparousness over 
its nearly related species in our country, but in Scandinavia 
it has to thank this peculiarity alone for its success in life, 
because the development of its young is rendered inde- 
pendent of the sun by it. The nectaries were probably at 
first useless to the flowers; from that moment, however, 
when the insects learned to know them as food reservoirs: 
and unwittingly insured cross-pollination by their visits to 
them, they became of the greatest importance and the indi- 
rect cause of the origin of the colour brilliance of the 
flowers. 

“There are organs of universal character which can be- 
come modified in most widely differing directions. Thus 
the tail of the mammals, originally a long, evenly-haired 
organ, can, without going through any very elaborate 
changes, be modified into a bushy steering-rudder of special 
use in climbing from branch to branch; or by the outgrowth 
of a terminal tuft be changed into a flying fan; or by the par- 
tial loss of the hair become a grasping organ, or a balancing 
organ, or an aid in leaping, a rudder in swimming, or a cover 
against rain and cold (Myrmecophaga jubata). The append- 
ages of crabs, the cirri of the annelids, and the teeth of mam- 
mals are further examples of a similar plasticity and capacity 


170 DARWINISM TO-DAY. 


for modification in the most manifold ways, in which the 
first stages are often of immediate use.” 

Following these suggestions as to the aid that selection 
may have from various helping conditions to make its 

starts, Plate discusses as further similarly help- 

afb ful conditions or auxiliary principles three most 
herited results important matters, namely, the effects of con- 
of use, from or- : eA eile 
thogenesis and tinted use on parts, the principle of orthogen- 
discontinuous = esis) and the tacts of sudden discontinuous 
variation. St Sa 

| variation. But as these three categories of 
biological phenomena and principles are exactly those, 
among others, which anti-Darwinians hold to be not aids 
to the selection theories, but to be the basis if not of actually 
replacing or substitutionary theories, at least of precisely 
those objections to the species-forming capacity of the strict 
Darwinian factors which have necessitated some of the 
principal concessions made by the Darwinists, it is obvious 
that Plate’s discussion of them is in itself simply the actual 
making of the concessions already noted as having been 
admitted by most Darwinians. Each of these categories 
of phenomena and principles is of course of much import- 
ance and interest, and they will all be found to be fairly fully 
set out in the chapters following this one. _ 

Plate’s answers to the second important objection, namely, 
that selection relies too much on chance and is therefore 

pains Xe improbable and inexact, may now be noted. He 
the objection | distinguishes two phases of this objection. The 
aeeanie ot first he expresses as follows: “It is highly im- 
selection on probable that for the progressive development 
Pe Ni or perfecting of an organ there will always 
appear just at the needed time the variation necessary for 
selection, that is, the exactly needed adaptive modification.” 
The second phase is: “It is highly improbable that in the 
development of a complicated organ, or body-part, or in 
the perfecting of a changing adaptation the numerous indis- 


DARWINISM DEFENDED. | D7 


pensable modifications will appear in such a series that a 
harmonious correlation of the single variations will be 
possible.” 

Referring especially to the first phase of the general ob- 
jection he says: 

“Thus this doubting query is, why do there always appear 
just the right variations at the right time? Or, somewhat 
differently expressed, in the words of Cope, ‘since the 
number of variations possible to the organism is very great, 
the probability of the admirably adaptive structures which 
characterise the latter having arisen by chance is extremely 
small.’ | 

“Whoever expresses such doubts unwittingly hitches the 
wagon before the horse. Selection directs itself according 
to the variation, not variation according to 

Selection fol- ; sur axesse : - 
lows variation, Selection. If the variability is large,. selection 
not variatim has a large choice; if the variability is small, 
selection. ; : 

then there are but few lines of evolution open. 
Experience teaches that in general, the variability of organ- 
isms is very large, that it occurs both quantitatively and 
qualitatively in such pronounced manner in all individuals 
of a species that it can be readily recognised without re- 
course to complex methods of investigation, and that no 
characteristic (size, form, colour, numerical relation, consti- 
tutional vigour, instinct, life-habit) is free from it in any 
life stage from egg to last drawing of the breath. It is 
precisely to this variability expressing itself in the most 
manifold ways and combinations that is to be ascribed the 
condition that any individual as such is, usually, readily 
to be distinguished from other individuals of the same 
species. It results from this that the individual variation is 
indeterminate and undirected, or better expressed, universal 
and all sided, and that at any given moment the exactly 
needed modification will always appear in a number of indi- 
viduals of any species rich in individuals, provided that 


Ee DARWINISM TO-DAY. 


the needed variation can be produced through a slight ad- 
vance or progressive change. Naturally it is not sufficient 
if the variation appears in only a few isolated individuals, 
but it is necessary, for the modification of the species, that 
this variation occur in so many individuals that it will not 
be extinguished through interbreeding but on the contrary 
will be perpetuated. In other words selection works, except 

Dek AO pais in scattered cases where single or Tare varia- 
with plural vari- tions are specially favoured by accidental iso- 
aan! lation, not with single but with plural variations. 
or varieties. Through this the host of variations is im- 
mensely reduced as far as they come into consideration as 
handles for selection, and of course only in this sense is 
there any reason at all for the query as to whether we can 
assume that the right variation will always be present at the 
right time. The answer can only be, certainly not always: 
many promising beginnings must always be checked in the 
germ or at half-way, but in infinitely many cases the needed 
plural variation will appear, because the same external 
factors change a whole group of animals simultaneously 
so that progress is possible. But, it goes without saying, 
only a slow advance is conceivable on this basis. 

“One must not, for the rest, forget that the same condi- 
tion of selective worth may be reached simultaneously 

through combinations of different peculiarities, 

Same selective : 
valuemaybe and that the same effect may be attained by 
attained in dif- yarious means, both of which facts render it 
ferent ways. : : 4 2 

importantly easier to get this selective worth. 

When pursued by an enemy one individual of the harassed 
species may save itself by a quick leap, a second through 
sharp ears, a third by sharp eyes. Wallace rightly explains 
that the necessity for a giraffe in times of famine is only to 
reach as high as possible in the trees, and that different 
means may avail for this, as a longer neck, long legs, or a 
long tongue, all of which may eventually come to be correl- 


DARWINISM DEFENDED. 73 


atively increased. The individuals which survive by these 
aids may then later, through inter-crossing, exchange their 
advantages and so lead to the production of a mean type 
that shows a slight advance over earlier conditions in all 
three organs. Mammals can protect themselves from flies 
in various ways, either by a thick fur (bears), by reflexive 
twitchings of the skin muscles (horse), by tails with tufted 
ends (many hoofed animals), by a long neck which can bend 
sideways so that the animal can reach any part of its body 
as far as the hips (guanaco, stag) or finally by eyelids and 
long movable ears, which restrain the flies from the easily 
injured eyes. These means of protection from insects play 
an important role in determining the habitus of many mam- 
mals, and permit the conclusion that selection has been 
instrumental in producing this habitus. Here, also, it is 
possible for several of these means to be possessed at once 
by the same animal, as in the case of the guanaco with its 
long hair and elongate neck. It is absolutely necessary for 
molluscs that live between tide-lines to have some means of 
resisting the force of the surf. Many species possess this 
means in their small size which allows them to crawl into 
crevices and cracks in the rocks, but most of them have 
developed a strong pedal sucker and a low roof-like uncoiled 
shell which presses close to the rock surface and over which 
the water flows without exerting any strong lateral pres- 
sure. This is the case, for example, with Patella, Fissurella, 
Chiton, Concholepas, Siphonaria, Gadinia, Calyptra, and 
others. All three of these means of safety can come into 
play simultaneously in selection, but it suffices when any 
given individual possesses any one of these means in suffi- 
cient degree of development. 

“T shall note here several other examples which show 
how related species reach the same advantage in the strug- 
gle through different means, for we can assume from these 
facts that also the individuals of the same species often 


174 DARWINISM TO-DAY. 


escape the same dangers in the struggle for existence by 
means of different means. And by this the probability is 
made greater that the ‘needed variation’ appears at the 
right time. The differing characteristics of this sort will 
later lead, through crossing, to the formation of a mixed 
type, or, if the competition grows ever sharper with the 
course of time, they will produce a separation of the species 
into varieties (eventually species) with differing habits of 
life, or finally they may meet in direct competition or strug- 
gle with one another. The good flyers among the birds all 
have long wings, but in some it is the fore arm which is 
specially lengthened (cuckoo, goat-sucker, pigeon), in others 
the hand (terns, humming-birds, eave swallows), and in 
still others the upper arm (swan).—While Tapirus ameri- 
canus, like most mammals, drives the flies away from its 
eyes by throwing down the eyelids, Tapirus indicus accom- 
plishes the same thing by a strong rotation of the bulb of 
the eye. Elephas africanus seizes very small objects with 
its proboscis-fingers, while the Indian elephant lays the front 
end of the trunk laterally on the ground, grasps the object 
between the skin-folds, lifts it up high in this way, and 
only then allows it to fall into the tip of the proboscis.— 
Poulton has shown by several examples that in cases of 
mimicry the same effects may be got in very different ways. 
The glass-like transparency of the wings, for example, is got 
in the Heliconid genus Menthona by a considerable dimi- 
nution in size of the scales, in the Danaid /tuna tliona through 
the absence of most of the scales, in Castnia linus var. heli- 
conoides, through the absence of pigment in the scales, which 
are as large and numerous as usual, in the Pierid Dismor- 
plia crise through the smallness of the scales, and finally in 
the night moth Hyelosia heliconoides by the absence of pig- 
ment and lessened number of the scales.” 

Plate next offers a detailed explanation on strict Darwin- 
ian grounds of how such an extraordinary condition of 


—— 


DARWINISM DEFENDED. 175 


mimicry can be brought about as the famous case of Kal- 
lima, the butterfly that simulates in colour, shape, and inti- 

mate details of pattern such as veins, flecks, 
Saba of fungus spots, etc., a dead leaf with such fidelity 

as to make it the wonder of every one who sees 
it and the classic example of the possibilities of such protect- 
ive resemblance. And he shows well that whatever diffi- 
culties selection may have in its necessary dependence on 
the chance occurrence of the proper numerous and neces- 
sarily simultaneously appearing variations to explain the 
gradual development of such a specialisation, the only other 
explanations so far offered are even more ludicrously de- 
pendent on “luck.” Piepers,” the most active and polem- 
ically vigorous of all special opponents of the Darwinian 
explanation of protective resemblance and mimicry, says: 
“Chance alone can bring about such a correlation.” As 
Plate well says, “It is not without its comic aspect that a 
violent antagonist of the selection theory should be found 
clinging to the same safety-anchor ‘chance,’ that usually 
is the constant reproach of the Darwinian... . . It would not 
be difficult,” continues Plate, “to refer to still other examples 
to show that a needed selective value can often be attained 
at the same time by the individuals of a species through 
various means, by which the probability that this type of 
adaptations can arise is correspondingly increased. But 
one point should never be forgotten and that is it is always 
first the variability, and second the selection. If no varia- 
tions appear there can be no progress, and if the struggle 
for existence were too severe the [non-varying] species 
would die out. Strictly speaking, the question, how is it 
possible that the right variations can be relied on to ap- 
pear at the right time? is really inverted and therefore 
incapable of receiving a correct answer. One can only 
say: If a complex adaptation has arisen through selec- 
tion, then it is certain that the necessary modifications. 


176 DARWINISM TO-DAY. 


needed for success in the struggle for existence were not 
wanting.”’ 

We come now to the second phase of the general objec- 
tion, as analysed by Plate; viz., the assumed improbability 

that during the course of the development 

Answer tothe (evolution) of a complicated organ or whole 
claimed improb- ; ; 
ability ofthe | body-part, or during the perfecting of a chan- 
Yeti bet ging adaptation, the numerous necessary varia- 
tions neededin tions will occur in such a successive series as 
co-adaptive to make possible an harmonious correlation of 
structures, 

the various single variations. Plate writes as 

follows: “This objection has been, as is the case with the 
objection just discussed, raised by many students of evolu- 
tion as Spencer, Wigand, Nageli, and is in principle not 
different from the previous objection, but only presents an 
elaboration of it. It concerns, first, the numerous single 
variations which are necessary if a single complex organ (as 
an eye) or a whole body-part with its various organs and 
tissues (for example, the neck of the giraffe, the fore body 
of the elk) ofa single individual is to be raised to a higher 
stage of adaptiveness; and, second, the perfecting of inter- 
dependent adaptations in different individuals. As example 
of the latter category I may mention the corolla of flowers 
and the proboscis of insects which cross-pollinate these 
flowers, the male and female copulating organs of many 
animals, as those of the Papilionide, the adaptations of 
myrmecophilous and termitophilous animals in relation to 
their hosts, also those of symbiotic (parasitic or mutualistic) 
species relative to their companions, and, in cases of mimicry, 
of the mimicking species relative to the protected species. 
When one of the species, party to such a mutual adaptation, 
changes, the other as a rule must also. There arises from 
this the query : how, in such cases, is there possible the neces- 
sary coadaptation (coordination), that is, the harmonious 
change of the parts which produce the interdependent physi- 


DARWINISM DEFENDED. i) 


ological or biological phenomena, whether these exist in a 
single individual or in two? How does it come that when 
the antlers of the giant stag become larger and larger, the 
skull bones become thicker and the neck tendons and the 
fore legs stronger (Spencer)? With the gradual lengthen- 


ing of the giraffe’s neck the skeletal system and with it || 
numerous other closely-related internal organs have to be- 
come larger simultaneously. Hundreds of small modifica-/; 
tions are necessary. How does it happen that all come off 


exactly as is necessary? When the flowers’ cups for any 
reason become deeper the insects must develop longer 
proboscides in order to reach the nectaries in the bottom of 
the cup. Simultaneously the sucking apparatus of the 
cesophagus must change. How does it happen that these 
modifications in two different organisms, in an animal and a 
plant, occur part passu? 

“In order to satisfy these questions of doubt Darwin and 
Wallace have referred to the domesticated animals as the 
best proofs that such coadaptations are possible. A grey- 
hound, a bulldog, a dachshund, a tumbler pigeon, a race- 
horse, have had to pass through a long series of numerous 
changes in the most various organs, in order to reach their 
present form, and yet all these variations have appeared 
one after the other in such a way as never to endanger the 
vital vigour, for man would never have chosen weakly ani- 
mals for breeding purposes. In artificial selection, there- 
fore, coadaptations are possible in almost infinite variety, 
and it can fairly be asked if such favourable conditions are 
not also possible in nature. This query must, a priori, be 
answered in the affirmative, for man is not able either to 
make more easy or to hasten the appearance of coadapta- 
tions : he can only hold on to those which once appear, and 
this can also be done by the struggle for existence in those 
cases in which the coadaptive variations are of vital import- 
ance. The real difference lies, therefore, in the fact that 


ate asta 


aeerteg 


| 


178 DARWINISM TO-DAY. 


man can make a beginning with ever so slight an advance; 
nature only with such simultaneous changes as are of suff- 
cient grade or degree to be of selective value. And so far 
in this discussion nothing has been offered to show how this. . 
condition is to be reached.” 

To attempt to get at an explanation of the actual means 
by which this necessary condition is attained, Plate believes it 

Plate’s belief ecessary that one should make ciear just what 
in the possibility standpoint he takes on the vexed problem of 
of the inheri- ; : : : 
tance of acquirea the inheritance of acquired characters. With- 
characters. out going into Plate’s long discussion of this old 
subject, it is sufficient to say that he reaches the conclusion 
that the inheritance of acquired characters is not proved 
not to be possible, and hence that it may occur. And, for 
himself, he expresses the belief that acquired somatic char- 
acters can be and are inherited. From this point of view, he, 
consistently with Darwin’s own position, finds an answer to 
the objection touching the necessity of a repetitive cumulat- 
ing appearance of certain definite kinds of variation for the 
basis of the development of coadaptation, by invoking the 
Lamarckian factor of the inheritance of the effects of use 
and functional stimuli. Which refuge is of course not open 
to the modern strict selectionists, the neo-Darwinians. 

Now, as may be imagined, when the Darwinians them- 
selves are of various minds about the value of the answers 
to this objection, when these answers are based on a strict 
selection basis, they are not very convincing to anti-Darwin- 
ians. In general they rest on various observed facts and 
deduced assumptions which may be roughly classified into 
several groups. First, the facts of simultaneous correlative 
variation, or the fact that organs or parts which function 
together, very often vary in the same general direction. For 
example, if two leg or arm bones become longer the muscles 
attaching to these bones also become longer (since the 
attachments are not changed). The supplying blood-vessels 


DARWINISM DEFENDED. 179 


and nerves also lengthen. Numerous observations by 
breeders show that in each organism there resides a capacity 
of self-regulation, up to a certain degree, which produces a 
harmonious growth and variation of inter-dependent parts. 
If a plant is removed to richly fertilised soil it will grow to 
great size, in the course of which growth all parts are pro- 
portionally changed so that the general habitus of the plant 
remains the same. If one allows insect larve to live on very 
short food rations, the adult insects will be unusually small 
but with all the organs of their usual relation to each other 
as to proportional size. Thus it seems that the single organs 
are definitely correlated with one another so that in their 
growth they maintain their relative characteristics. “I 
have,” says Plate, “called this form of organic Zweckmdassig- 
keit the unity of organisation.” If this quality or capacity 
is lacking in an individual then it develops into a cripple, a 
monster, and is killed out by selection. Therefore, if the 
neck of the giraffe varies so as to be longer, one may fairly 
assume that, in the case of many individuals, at least, all 
parts of the neck will share in this variation, although there 
will naturally be slight individual varyings inside of this 
general variation. And if the antlers of the stag vary 
towards a larger size there will simultaneously appear the 
necessary increase in calcareous materials for all parts of 
the skull, so that the whole skull will be correspondingly 
heavier and stronger. 

“The process of evolution may be assumed to be, as it was 
by Darwin, very slow, so that plenty of time is allowed to 
selection to produce the necessary coadaptations which may 
be wanting in the earlier stages of the development. In 
the case of the enlarging of the stag’s antlers there may have 
been wanting at first the necessary congenital strengthen- 
ing of the neck muscles but this would come to exist through 
use. The effects of use would increase, however, only to a 
certain point, and there would finally come a time when the 


180 DARWINISM TO-DAY. 


heavy antlers could be supported only by those individuals 
which had received a strengthening of the neck muscles 
through congenital variation. All others would be killed out. 
“The already discussed principle of the attainment of 
selective value for a certain advantage by various means, 
comes also into play in this connection. In time of drouth it 
is important to the giraffe only that it can reach a certain 
height on the trees; whether this height be reached by the 
aid of a longer neck or higher shoulders or a specially 
elongate tongue is indifferent. Through inter-breeding 
these various advantages may be later united. There is 
always resulting, as Wallace *’ has said, “Selection of the 
capacities or qualities resulting from the infinitely varied 
combination of variations that are always occurring.’ 
“Recently Weismann ** has presented the principle of 
germinal selection as explaining coadaptive specialisations, 
Plate's dis. 4 SO that he is evidently not satisfied with the 
beliefin Weis- sufficiency of the three aiding explanations 
ram dea already given. I hold this germinal selection,” 
selection. says Plate, “to be a false conception, and there- 
fore do not here refer to it further. It will be discussed in 
detail later.” (This later discussion of Plate’s is a detailed 
and effective destructive criticism of the theory.) 
“Weismann, in his “Lectures on the Theory of Descent, 
outlines in detail his theory, proposed several years before, 
win that amphimixis (bisexual parentage) is so 
principle of widely prevalent in both the plant and animal 
amphimixis. kingdoms, because it serves as the spring of 
individual variations. A considerable part of the chromo- 
somes of the egg-cell is removed by the discharge of the 
polar bodies, and the same results from the reduction divi- 
sions of the sperm-cells. By this the possibility is created 
of producing, through the fusion of the germ-cells, very 
various combinations of the hereditary tendencies and, there- 
fore, an actual high degree of variability in the offspring. 


912 


DARWINISM DEFENDED. 181 


‘Because in each reducing division of the germ-cells their 
ids are lessened by one-half, the possibility exists of gradu- 
ally removing from the germ-plasm of the species the ids of 
the disadvantageous variations, for in each generation the 
offspring of the disadvantageous id combinations are ex- 
tinguished [by selection], so that from generation to gen- 
eration the germ-plasm gradually becomes purified of the 
disadvantageous ids, while the favourable combinations 
which amphimixis produces are retained, and there finally 
remain only the advantageously varying combinations or, at 
any rate, those in which the advantageously varying deter- 
minants are in the majority and therefore have the most 
influence’ (Vol. II, p. 222). This conception of the sig- 
nificance of the reduction divisions of the maturing germ- 
cells and their fusion is very suggestive, and, theoretically, 
there is little to be objected to in the idea that the differences 
thus created can be used by personal selection for the pro- 
duction of harmonious coadaptations. Indeed, with this 
explanation in hand, it is obvious that the theory of germinal 
selection is superfluous for the explanation of coadaptations 
if we may assume that there is always a great mass of 
material in the individual variations, for the possibility of 
varying combinations of these requires no further expla- 
nation.”’ 

For the most part it is obvious that Plate, and with 
him other fair-minded Darwinians, recognise fully the 

Plate recog. cogency of the objections against Darwinism 
nises the weight based on the inutility of slight variations, on 
of certain objec- : 
tinein Darwin tie. occurrence) and persistence’ of hosts, of 
ism, trivial or indifferent species differences, and 
on the difficulties presented by the demands of a controlled 
appearance of variations necessary to the development of 
coadaptive structures and functions, so that they are inclined 
to make the concessions which I have referred to in the 
beginning (chapter vi) of this presentation of ‘Darwinism 


182 DARWINISM TO-DAY. 


Defended.” With these concessions made it is necessary to 
call to the aid of the selection theory, if it is still to be con- 
sidered an important factor in species-forming—these con- 
cessions do not, of course, invalidate the claims of selection 
to be the all-important final factor in determining the 
general course of evolution, by encouraging or restraining 
the various general lines of descent—certain auxiliary and 
aiding theories or explanations. Such helps to selection are 
to be found especially in isolation, organic selection, and 
the Weismannian theories of panmixia and germinal selec- 
tion. The outlining of these theories will form the con- 
tents of our next chapter. 


APPENDIX. 


1 Plate, Ludwig, “Uber die Bedeutung der Darwin’schen Selec- 
tionsprinzip,’ 1903. 

* The question, what is meant by “selective value,” has been dis- 
cussed by Conn (‘Method of Evolution,” pp. 83-86, 1900), as fol- 

Conn’s discus- lows: “How useful must a character be to be of 
sion of selective selective value? Such a question it is, of course, im- 
value. possible to answer. The preservation of any particu- 
lar character is not an isolated matter. It is not single characters 
that are preserved, but a combination of many characters together. 
The survivor is the animal showing the best combination of char- 
acters. It may even have some harmful ones, provided the useful 
ones predominate. The rattle of the rattlesnake has at times doubt- 
less been of a disadvantage to its possessor, and has caused the 
death of hundreds of thousands of individuals. It is doubtless 
possible to show, as Darwin did, that it has also been of value to 
the animals. But how are we to decide whether its use or dis- 
advantage is the greater, except by the theoretical conclusion that 
it must on the whole be useful or it would have been eliminated? 
The whole study of utility is sure to result in an unsatisfactory 
circular logic, something as follows: The survival of the fittest is 
a law. If an organ be not useful it could not have been developed 
by natural selection. Therefore, all organs and all characters must 
be useful. Since in such a problem no one can prove a negative, 
this position cannot be disproved; but it is certainly not very satis- 
factory. 


DARWINISM DEFENDED. 183 


“But with all this criticism of utility it must be recognised that 
the agency of utility as determining survival is becoming more 
significant as discussion proceeds. We have seen that it must be 
admitted that all characters to be affected by the principle of 
survival, must have selective value: 7. e., must affect the matter of 
life and death. But this demand does not prove to be so serious 
when we recognise that natural selection works upon general 
averages rather than individuals. Those who find the selection 
principle such a great factor insist that all characters have selective 
value if they have any value at all. If a character has the value 
of even rendering its possessor a little more comfortable, they tell 
us it will eventually be subject to the principle of survival at the 
expense of non-favoured animals. The substitution of old types 
by new ones is not a matter of a single generation, but many 
generations. In such a long history there must be innumerable 
conditions where any character, even the slightest, may have been 
of use enough to give its possessors an advantage over others. It 
is not necessary to believe that a character should preserve its 
possessor, while all non-favoured individuals perish, in order to 
consider that the character has selective value. Considering that 
the origin of species is a matter extending over hundreds of years 
and many generations, even little things will count in the long run. 
If an animal has a slight advantage over another, which simply 
gives it more comfort and enables it to obtain its food with a little 
less exertion, this may tell permanently in the struggle, since such 
an individual will have more energy to put into reproduction, and 
hence may leave a larger number of offspring. The other non- 
favoured individuals may not, indeed, be exterminated without off- 
spring, but may simply produce less offspring. In this struggle for 
permanency, the individuals which have the largest number of 
offspring, other things being equal, will inevitably come out ahead, 
and the others in time disappear. 

“An example will make this clearer. A difference of an inch or 
two in the length of a cow’s tail seems a matter decidedly too 
small to base the selection principle upon. Can it be imagined 
that the lengthening of the tail by a couple of inches can be of 
selective value? Can we honestly believe that these two inches will 
determine that the longer-tailed cow will live and produce off- 
spring, while the shorter-tailed individuals will die? Only thus, 
however, can we assume that the tail has been developed by natural 
selection. Now this example, which seems to be an extreme case 
of slight utility, may show us how it is possible, upon the principle 
of the selection of averages, to conceive that characters of slight 
use may be preserved by natural selection. It is not necessary to 


184 DARWINISM TO-DAY. 


suppose that the long-tailed individuals are preserved by this extra 
couple of inches at the expense of the shorter-tailed individuals 
in order that the character may be within the reach of natural 
selection. If the animals are troubled by insect pests, it is cer- 
tainly a matter of convenience to them to have a tail long enough 
to brush off the flies, and the longer tail, within certain limits, will 
be more useful than a shorter one. It is not likely that this will 
preserve the life of a single individual, but it will follow that the 
animals with longer tails will be less irritated by insects than 
those with shorter tails. Now, although this would not affect the 
‘matter of life and death, a nervous irritation would pretty surely 
interfere with the reproductive efficiency. An animal that is con- 
stantly bothered by insects will have less nervous energy to devote 
to reproduction, and, therefore, such a constantly irritated animal 
would be likely to be somewhat less prolific than one less irritated. 
From this it would follow that the half of the animals with tails a 
little longer than the average, would be pretty sure to leave a some- 
what larger number of offspring than the half whose tails were 
below the average. But a slightly increased fertility of this sort 
would, in the course of a few generations, see the long-tailed animals 
becoming more and more numerous, until they would eventually 
replace the others.” 

* Dodel-Port, A., “Wesen und Begriindung der Abstammungs- 
und Zuchtwahl-Theorie in zwei gemeinverstandlichen Vortragen,” 
1877. 

* The tsetse-fly (Glossina sp.), long notorious as a_ terrible 
pest of cattle in Africa, produces its ravages by disseminating 
(through biting, 7. e., puncturing the skin) the specific causes 
(certain minute blood-inhabiting parasitic one-celled animals 
known as trypanosomes) of the plague called Nagana (fly dis- 
ease). 

* For an elaborate discussion of the principle of correlation (not 
bearing perhaps except in a general way on the point just at issue, 

Referencesto but of much general interest) see Radl, Em., “Uber 
papers on corre- die Bedeutung des Prinzips von der Korrelation in 
lation. der Biologie,’ Biol. Centralbl., Vol. XXI, pp. 4o1- 
416, 490-496, 550-560, 605-621, 1901. See also Webber, H. J., “Cor- 
relation of Characters in Plant-Breeding,” Proc. Amer. Breeders’ 
Assoc., Vol. II, pp. 73-83, 1906. 

* For examples see R. Meldola, ‘The Utility of Specific Char- 
acters and Physiological Correlation,” Proc. Ent. Soc., London, pp. 
62-92, 1896; also A. R. Wallace, “The Problem of Utility; are 
specific characters always or generally useful?” Jour. Linn. Soc., 
Vol. XXV, pp. 481-496, 1804. 


DARWINISM DEFENDED. 185 


7 Dohrn, Anton, ‘Der Ursprung der Wirbeltiere umd das Princip 
des Functionswechsel,”’ 1875. 

®*Cope, E. D., “The Energy of Evolution,” Amer. Nat., Vol. 
XXVIII, p. 205, 1894. I quote the following: “In considering the 

Binet aeroat dynamics of organic evolution, it will be convenient 
thabatirnl to commence by considering the claims of natural 
selection cannot selection to include the energy which underlies the 
make new char- process. That natural selection cannot be the cause 
eal of the origin of new characters, or variation, was 
asserted by Darwin,* and this opinion is supported by the following 
weighty considerations. 

“(1) A selection cannot be the cause of those alternatives from 
which it selects. The alternatives must be presented before the 
selection can commence. 

‘““(2) Since the number of variations possible to organisms is 
very great, the probability of the admirably adaptive structures 
which characterise the latter having arisen by chance is extremely 
small. 

“(3) In order that a variation of structure shall survive, it is 
necessary that it shall appear simultaneously in two individuals of 
opposite sex. But if the chance of its appearing in one individual 
is very small, the chance of its appearing in two individuals is 
very much smaller. But even this concurrence of chances would 
not be sufficient to secure its survival, since it would be immediately 
bred out by the immensely preponderant number of individuals 
which should not possess the variation. 

“(4) Finally, the characters which define the organic types, so 
far as they are disclosed by paleontology, have commenced as 
minute buds or rudiments, of no value whatsoever in the struggle 
for existence. Natural selection can only effect the survival of 
characters when they have attained some functional value. 

“In order to secure the survival of a new character, that is, of 
a new type of organism, it is necessary that the variation should 
appear in a large number of individuals coincidentally and suc- 
cessively. It is exceedingly probable that that is what has occurred 
in past geologic ages. We are thus led to look for a cause which 
affects equally many individuals at the same time, and continuously. 
Such causes are found in the changing physical conditions that have 
succeeded each other in the past history of our planet, and the 
changes of organic function necessarily produced thereby.” 

* Piepers, M. C., ‘““Thesen ttber Mimikry,” Verh. Internat. Zool. 
Cong., p. 350, 1902. 


* “Origin of Species,” ed. 1872, p. 65. 


186 DARWINISM TO-DAY. 


*° Wallace, A. R., “Are Individually Acquired Characters Inher- 
ited?” Fortnightly Review, Vol. LIII, pp. 490-498, 1893. 

11 Weismann, A., “Uber Germinal-Selection,’ Verh. Internat. 
Zool. Cong., 1806. 

** Weismann, A., ““Vortrage tiber Descendenztheorie,” 2 vols., 1902. 


CHAT Pr Rav TL 


OTHER THEORIES OF SPECIES-FORMING AND 
DESCENT CHEORIES AUXILIARY TOoSEERC- 
GION: 


To be considered now are two categories of (mostly) 
post-Darwinian theories, viz., those which have been offered 

Classification 2S alternative theories intended to replace more 
of other theories or less nearly entirely the selection theories, 
as auxiliary or : ; 
alternativeto and those other theories intended to serve as 
selection. auxiliary and supporting theories for Darwin- 
ism. Obviously these two kinds of theories * emanate from 
the two opposing biological camps. Several of these alter- 
native and auxiliary theories of species-forming have been 
referred to incidentally in the preceding two chapters, for 
the replacing theories constitute part of the strength of 
the anti-Darwinians, while the supporting theories are dis- 
tinctly relied on to help maintain the Darwinian front. The 
present chapter, then, is mostly a continuation of the pres- 
entation of “Darwinism Attacked” and “Darwinism De- 
fended,” which is given a separate place because of the 
special character of the argument with which it has directly 
to do, namely, the synthetic or theory-building side, instead 
of the analytic or theory-destroying side, and because of 
the probable advantage to the student and general reader 
wishing to understand and compare the general character 
and significance of the various new theories of species- 
forming with whose names, such as heterogenesis, ortho- 
genesis, metakinesis, geographic isolation, biologic isolation, 
organic selection, or orthoplasy, he occasionally meets in his 

187 


188 DARWINISM TO-DAY. 


general reading. As directly continuing the last chapter we 
may consider first those theories put forward, chiefly by 
Darwinians, as auxiliaries or supports of the selection 
theory. Then we may briefly take up those theories that 
have been advanced, mostly in recent years, as more or less 
nearly completely prepared to replace Darwinism as a sufh- 
cient scientific causo-mechanical explanation of species- 
forming and descent. 3 
The Weismannian Theories of Panmixia and Germinal 
Selection.,—Weismann has for years been the most con- 
| Ba amt spicuous of the neo-Darwinians, that is, of 
portant contribu. those who would free Darwinism from all taint 
tions to biology: Of Tamarckism—it should always be remem- 
bered that Darwin was inclined to attribute some degree of 
influence in species-forming to the Lamarckian factor of 
the inheritance of individually acquired adaptive charac- 
ters—and to make selection the all-sufficient and, indeed, 
sole factor in species-forming. His great services to biology 
in general and to the clearer understanding of the problems 
of heredity and descent in particular, are unquestioned and 
unquestionable. His careful investigation and illumination 
of the vexed question of the inheritance of acquired charac- 
ters, his definitive exposition of that point of view which 
distinguishes sharply in the individual between the germ- 
plasm (that particular protoplasm in the body from which 
the germ-cells, eventually new individuals, arise) and the 
soma-plasm (that which develops into, or gives rise to, the 
rest of the body), his development of the interesting and 
suggestive combinations of fact and theory designated by 
the phrase names “continuity of the germ-plasm”’ and “‘im- 
mortality of the Infusoria,’—these products of his investi- 
gating and philosophising mind prove him one of the ablest 
of modern biological scholars. They also make him the 
principal present-day champion of the selection theory. For 
all these expositions of fact and theory are of a nature to 


OTHER THEORIES OF SPECIES-FORMING. 159 


enhance the credit of selection and to discredit certain other 
species-forming theories, in particular the only one, namely, 
aa ae Lamarckism, which, until recently, has been in 
champion of any real sense a rival of Darwinism. Against 
5 ries Weismann then and against Weismann’s re- 
modelled kind of Darwinism, against his propaganda of the 
Allmacht of selection, the adherents of Lamarckism and the 
critics of selection have turned their sharpest weapons. The 
result of the struggle has been to compel Weismann himself 
to say: “Although the principle of selection appears to solve 
in simplest manner the riddle of the fitness (Zweckmdassig- 
keit) of all arising organisms (alles Entstehenden), yet it 
appears ever more clearly in the course of the further inves- 
tigation of the problem, that one cannot explain all with it, 
at least in its original limitations (dass man mut thm, in 
seiner urspriingliche Beschrinkung, wenigstens, micht 
ausreicht).”’ 

To support the selection theory in two of its weakest and 
most criticised places, Weismann has proposed two striking 
auxiliary theories, namely, the Theory of Panmixia, to 
explain the degeneration of functions and organs, and the 
more recent Theory of Germinal Selection, to account 
for the now practically generally admitted existence of 
orthogenesis or determinate variation and _ evolutionary 
progress along fixed lines even to the possible final dis- 
advantage of the organisms involved, and to account for 
the beginnings of variation and their maintenance until 
sufficiently developed to serve as handles for selection. The 
proposal by Weismann of the second theory, that of 
germinal selection, was the practical admission on his part , 
of the impotence of selection to initiate new lines of develop- ’ 
ment or descent. It was a concession on Weismann’s part }» 
of the justness of the demand for an evolutionary factor to — 


explain the beginnings of lines of development, whether of one 


new organs or new species. And there is no doubt that it is 


190 DARWINISM TO-DAY. 


the most ingenious mechanical explanation yet offered of 
the workings of such a factor. Indeed, Weismann, with 
characteristic ingenuity and capacity, has offered the be- 
lievers in orthogenesis that which they so far had not been 
able to get for themselves, namely, a possible causo-mechan- 
ical explanation of it. It should be noted that Roux’s theory 
of the battle of the parts (explained later) was a forerunner 
of, and undoubtedly the suggestion for, the theory of 
germinal selection. 
Familiar to all students of biology, and certainly not 
wholly unfamiliar to laymen, are those structures or parts 
in the body known variously as vestigial struc- 
ach pe tures, rudimentary or degenerate organs. The 
plain vestigial yermiform appendix in man is one; the eye of 
lath the mole is another; the functionless wing of 
the ostrich, the useless fore-feet of a milk-weed butterfly, 
_ and the splint bones of the horse, are others. Almost every 
animal kind possesses vestigial organs, and some kinds 
possess very many. Those in the human body make an 
amazingly long list. All these are organs, which have once— 
that is, in ancestors of the present particular organism 
—been well-developed and probably useful. But these 
organs now are useless or even harmful.. The human 
appendix vermiformis is harmful; the tiny fore-feet of the 
milk-weed butterfly are useless. Why do animals have 
such vestigial organs? Because they derive them by hered- 
ity from ancestors. But in these ancestors the organs were 
well developed and useful. How is it that the present 
organisms do not need the same organs? They have adopted 
new habits, or live in a new environment, or have developed 
other means of supplying the old want; in a word the organs 
, are superfluous. How is it that the organs have become 
thus degenerate or vestigial? This is the question that 
selection has difficulty in answering satisfactorily. Selec- 
tion can develop and specialise organs of use and advantage; 


OTHER” THEORIES OF (SPECIES-RORMING, Igt 


but how can it cause organs no longer useful and advan- 
tageous to degenerate? 

It is possible, perhaps, to explain the eradication of 
positively harmful organs by a process of negative or 
reversed selection. If an organ becomes actually harm- 
ful because of a change in life conditions, individuals. 
with the organ in poorest, least energetically functioning 
condition might be conceived to have an advantage and be 
preserved by selection to pass on to their offspring this 
less developed, 7. e., rudimentary or vestigial, character of 
the particular organ in question. But when the organ is 
simply only rendered useless by the change in life condi- 
tions, as when a species of fish or insect gradually comes to: 
inhabit deep dark caves and thus has no more use for its 
eyes, how does selection explain the degeneration? It really 
doesn’t, satisfactorily. So Weismann offers the theory of 
panmixia to account for it. This is, simply, that owing to# 
the cessation of selection in regard to the particular organ 
whose function is rendered no longer advantageous or 
necessary under the new life conditions—that this cessation | 
of selection is an obvious result of such a state of affairs 
was recognised by Darwin himself, and by other biologists— 
individuals born with this organ defective or in a condition © 
below the average, would not be necessarily killed by the’ 
rigours of the intra-specific struggle, and would therefore be 
as likely to mate and keep on producing offspring as the 
ones with the organ in average or above average conditions. 
This general participation of all kinds of individuals (all 
kinds, that is, as regards the state of the particular organ) 
in producing the next generation, and the continued repeti- 
tion of this general mixing, panmixia, would obviously lead 
to a reduction of the earlier high condition of development 
of the organ. Weismann thinks, or thought, it would lead 
to a steady degeneration of the organ. But few other biol- 
ogists, even those ardent selectionists anxious to find in 


192 DARWINISM TO-DAY. 


panmixia an explanation not involving the admission of 
any new organ-modifying factor, have been able to see how 
panmixia can do more than simply reduce the organ to a 
certain stage below the original state of greatest effective- 
ness. By resorting to mathematics several writers have 
determined the exact—unfortunately for their convincing 
character—several degrees of reduction or degeneration that 
will result from panmixia. The difficulty of explaining 
degeneration (to the degree in which it is manifest in thou- 
sands of known cases) on the basis of panmixia alone, is that 
there is included no factor or influence that would sum up 
or cumulate variations in a retrogressive direction any more 
than in any other. The Darwinian variations of the use- 
less organ would, by the law of error, simply keep the organ, 
thus abandoned by selection, swinging about a mean but 
little below the condition possessed by the organ at the time 
of its abandonment. If the organ were large enough, or of 
a character whereby it would entail a constant considerable 
disadvantageous expense of food material to maintain it, 
then selection might, on a basis of an advantageous economy 
of living, tend to reduce it to a non-disadvantageous size or 
character. But this disadvantage, although easily presumed 
by carrying out the rigour of the struggle to a logical ex- 
treme, cannot, in fact,—and biologists on the whole admit 
this,—in common sense be assumed. 
Lamarckism offers a perfectly simple and-perfectly effect- 
ive and satisfactory explanation of vestigial organs and the 
modus of their degeneration. But to accept this 
The Lamarck- ; Py 
jan explanation ™means to accept the basic principle of Lamarck- 
of vestigial ism, namely, the inheritance of acquired char- 
structures. par ° ; 
acters. And it is one of Weismann’s most con- 
spicuous positive achievements that he has demonstrated the 
unproved character of this theory. Lamarckism says that 
the first fishes to go into the dark cave suffered a partial 
individual degeneration of their eyes through disuse and 


OTHER DHEORIES -OF SPEGIES-FORMING, 193 


that this eye degeneration was inherited by their young, 
whose eyes, already bad, suffered further degeneration in 
their life-time through disuse, and that after comparatively 
few generations this cumulative actual morphologic degen- 
eration through disuse—and we know that unused active 
organs, as muscles, stimulus-perceiving parts, etc., do actu- 
ally degenerate in an individual’s life-time through disuse— 
would reduce the eyes to a very degenerate condition. Other 
cases of degeneration, especially of passive organs (1. @., 
where the organ’s condition was not so wholly a function 
of use or disuse, but of the direct moulding influence of 
extrinsic influences), are explained by Lamarckism on the 
basis of the inheritance of the results of the direct action 
or influence of environment on the organ. For example, 
the gradual disappearance of pigment (blanching) charac- 
teristic of many cave animals, would be explained by the 
absence of the extrinsic factor, light, which is necessary to 
stimulate pigment production. 

In necessarily closing this all too brief reference* to 
panmixia, it may be said that Weismann himself has in 
recent years recognised its unconvincing character; and that, 
Plate, a strong upholder of selection, in a most careful 
weighing of panmixia, finds it capable of explaining fung- 
tional degeneration but not any actual considerable mor- 
phological rudimentation. 

The Theory of Germinal Selection was proposed by Weis- 
mann in 1895, more definitively in 1896. Plate introduces 

Mec aante his discussion of this theory as follows: “Its 
theory ofger- aim is the rehabilitation of the selection princi- 
se ple. It shall overcome all objections and doubts 
which have been raised against the selection theory and shall 
act as the magician’s wand to clear all difficulties from its 
way. Its strength shall avail in four directions. First, it 
shall explain how not only degeneration (physiological) but 
rudimentation (morphological) occurs in panmixia; second, 


194 DARWINISM TO-DAY. 


why exactly those variations needed for the development of 
a certain adaptation appear at the right time; third, how 
correlation of adaptation comes to exist; and fourth, how 
variations are able to develop orthogenetically along a defi- 
nite line, without depending on the necessity of a personal 
selection raising them step by step.” Weismann himself 
refers to the theory as “a spring of definitively determined 
variation.” In 1902, Weismann further applied the theory 
to the explanation of monsters, and other cases of terato- 
genesis, of “sports’’ (sudden or large discontinuous varia- 
tions), of suddenly appearing sex-characters, of specific 
talents, and still other heretofore unsatisfactorily explained 
phenomena. 

In defining the theory of germinal selection we come at 
the very start to a difficulty based on the fact that little or 

no reference has heretofore been made in this 

The physical hook to certain various theories or speculations. 
and chemical Pp 
structure of as to the ultimate structure of protoplasm, espe- 
protoplasm. ; 

cially the protoplasm of the germ-cells. In 

recognising protoplasm as the “physical basis of life’ (Hux- 
ley’s phrase), biologists have naturally tried to find in 
its actual physical make-up some clue to its marvellous 
capacities. The highest powers of our best microscopes, 
however, reveal little more of this intimate physical struc- 
ture than does our unaided eye. Probably the colloidal char- 
acter of protoplasm, that is, its amorphous, non-crystalline, 
viscous condition, is the most important physical fact about 
it revealed by our closest examination. But this apparent 
_ simplicity of physical structure is very unsatisfying to most 
| biologists, and they demand the assumption of an extremely 
'complex structure; a subdivision of germinal protoplasm 
_ into structural units and groups of units, just as the chemist 
assumes, in his atomic theory, a subdivision of substances 
into molecules and atoms. These protoplasmic units are, 
of course, invisible; like the atoms, they are beyond the see- 


OTHER THEORIES OF SPECIES-FORMING. 195 


ing of our microscopes. This nearly unanimous demand 
on the part of biologists for a complex physical structure 
of protoplasm, depends largely on the fact that our present 
knowledge of the chemical constitution of protoplasm offers 
absolutely no explanation of its capacities. We know that 
protoplasm is composed of certain familiar elements, pres- 
ent in certain proportions. But beyond that nothing; the 
actual chemical relations of these component elements are 
too complex for analysis. Besides, certain observations of 
the processes of protoplasmic behaviour suggest strongly 
the workings of a machine whose effectiveness lies in its 
physical make-up. Finally, the phenomena of heredity 
seem to admit of no other explanation than the assumption 
of a composition of the germinal protoplasm out of myriads 
of structural units actually representing the myriads of cells, 
or groups of cells, of the fully developed body. 

Ever since protoplasm has been recognised as the physical 
basis of life, therefore, and ever since the germ-cells have 
been recognised not to be miniature men and women, but, 
as far as the eye and microscope go, masses of primitive 
protoplasm differentiated only into cell-plasm, nucleus, and 
nuclear parts (chromosomes, centrosomes, nucleoli, etc.), 
there have been “atomic” theories of protoplasmic struc- 
ture. Unfortunately for the standing of any one of these 
theories, each working biologist seems to have made one 
for himself, so that instead of one universally accepted, 
hence usable and useful, atomic or unit theory such as the 
chemists have—and the modern physical chemists seem 
to be rebelling even against that,—biology has had a host 
of protoplasmic unit theories of which the one we have here 
specially to refer to is known as Weismann’s theory of 
biophors and determinants. Several of the better known or 
more ingenious of these theories are outlined in very sum- 
mary fashion in the appendix * of this chapter. What we 
need now to know of biophors and determinants in order to 


\) super-molecules, as complex groups of chemical molecules, 


v 


j 


i 


; 


196 DARWINISM TO-DAY. 


understand the theory of germinal selection, is this: Weis- 
mann conceives the protoplasm of the cell nucleus to be 
composed of units called biophors—these biophors can also 
migrate out into the cytoplasm surrounding the nucleus— 
which are the bearers of the individual characters of the cell. 
The total character of any cell, its form, make-up, and spe- 
cial properties, is determined by the totality of its biophors. 
These biophors are not, however, such simple structures as 
the atoms of the chemist ; indeed, they are to be looked on as 


of determined character and arrangement. Moreover, as 
‘these biophors are life-units, they possess the essential char- 
acteristics of life, that is, the capacity to assimilate food, 
to grow, and to reproduce themselves by division. The num- 


\ ber of different biophors is almost inconceivably enormous ; 


| for it must equal the possibilities of variety in character 
exhibited by, or capable of being exhibited by, all the cells 
\of the body. But as each biophor is made of many complex 
molecules which may vary among themselves, and also vary 
in their structural relation to each other inside the biophor, 
it is not difficult, perhaps, to imagine the possible variety of 
biophors to be equal to the possible variety of cell char- 
acters. These biophors are conceived to be united into 
fixed, indissoluble groups called determinants, each de- 
terminant containing all the biophors necessary to deter- 
mine the whole character of any one kind of cell. Like 
the biophors the determinants can assimilate food, grow 
and multiply by division. While in each specialised body- 
cell there needs to be but a single determinant, namely, 
one of the special kind conforming to the special kind 
of cell, in the germ-cells there must be conceived to be 
every kind of determinant which may be found in all 
the body-cells taken together. But, fortunately, by virtue 
of the determinants’ capacity for multiplication it is 
not necessary to assume that there exists in the germ a 


OTHER THEORIES OF SPECIES-FORMING. 197 


determinant for every cell that is to develop in the body, but 
only one for every different kind of cell; all cells exactly 
alike can be supplied with similar determinants by the multi- 
plication of the proper kind. Now Weismann’s theory of 
germinal selection rests upon the assumption of a competi- 
tion or “struggle” of the determinants in the germ-plasm 


for food and hence for opportunity to grow, to be vigorous, . 


and to multiply. The germ-cells derive their food, as do 
the other cells and tissues of the body, from the general 
food streams circulating around and through the cells. 
Weismann, recognising the absolute principle of slight varia- 
tion everywhere in Nature,—it is practically impossible to 
conceive of identity,—believes that the initially slightly 
stronger or more capable determinants will be able to take 
up larger supplies of food, even to the extent of lessening 
the supply for neighbouring determinants, perhaps to the 


degree of starvation. Indeed he suggests a reason for the | 
initial slight variations in vigour of the determinants in the | 
probability that the food will reach the various determinants — 


in slightly, purely fortuitously, variable quantity, so that 
the first inequality in vigour of the determinants will depend 
on the fortuitous variability of food supply, while there- 
after the variability in the determinants thus produced will 
enable the stronger ones to draw to themselves or take up 
more food and thus accumulate determinately the initial 
fortuitous inequality. 

Thus when the germ-cell begins its development into 
a new individual those kinds of cells, tissues, and organs 
will be best developed whose determinants were most suc- 
cessful in the struggle for food, while other parts of 
the body may be made smaller or even may not appear 
at all because of the starvation of the determinants re- 
sponsible for the cells which should compose them. Also 
these better-developed, larger, more vigorous determinants 
of one generation will hand on to the germ-plasm of the 


eal 


198 DARWINISM TO-DAY. 


next generation strong and extra-vigorous daughter deter- 
minants. For any determinant in the germ-plasm of a fer- 
tilised egg-cell has not alone to furnish determinants which 
shall control the development of body-tissues and organs 
of the individual which develops from this cell, but also to 
furnish daughter determinants for the new germ-plasm of 
this individual. This will result in a repetition of the 
extra-development in the next generation of the same organs 
as were strongly developed in the first generation, and the 
under-development of the same organs as were weak or 
wanting in the first generation. Which process continued 
is simply determinate variation, that is, variation along 
. fixed lines without reference to personal selec- 
lesa fe tion. Now when this variation becomes so 
indeterminate marked that it is of life-and-death advantage 
variation: ¢ ‘ : eo goes . 
or disadvantage in the life of the individual, it 

will immediately become subject to the control of personal 
natural selection, and under the influence of this dominant 
factor in determining adaptation, either be further fostered 
and fixed or be extinguished. If the increasing organ or 
part due to germinal selection be one whose increase is 
advantageous to the individuals possessing it, then natural 
selection will preserve those individuals and the germinal 
advantage of the determinants of this part will be steadily 
increased, as the size and power of assimilation of the 
determinants correspond to the size and vigour of the part. 
By this theory Weismann believes that he has explained 
away one of the most potent objections to natural selection, 
viz., that it is necessary to assume, for the effective work of 
selection, the timely appearance of the proper variations 
necessary for the continued advantageous modification of 
apart. “Knowing this factor, we remove, it seems to me,” 
writes Weismann,’ “the patent contradiction of the assump- 
tion that the general fitness of organisms or the adaptations 
necessary to their existence, are produced by accidental 


—_ —— 


OTHER THEORIES OF SPECIES-FORMING. 199 


variations—a contradiction which formed a serious stum- 
bling-block to the theory of selection. Though still assum- 
ing that primary variations are ‘accidental,’ I yet hope to 
have demonstrated that an interior mechanism exists which 
compels them to go on increasing in a definite direction, the 
moment selection intervenes. Definitely directed variation 
exists, but not predestined variation running on independ- 
ently of the life conditions of the organism as Nageli, to 
mention the position that the most extreme advocate of 
this doctrine has assumed: on the contrary, the variation is 
such as is elicited and controlled by those conditions them- 
selves, though indirectly.” 

Obviously Weismann in his theory of germinal selection 
has preserved the actuality of a struggle and a selection, but 
with a “rehabilitation” of natural selection in the real Dar- 
Winian meaning and only fair application of the phrase the 
new theory has nothing to do. It is, much more, a distinct 
admission of the inadequacy of natural selection to do what 
has long been claimed for it. It is the first serious attempt 
at a causo-mechanical explanation of a theory of ortho- 
genesis, that is, variation along determined lines. 

As to our acceptance or non-acceptance of such a theory 
we need say little. It consists of two purely speculative basic 
assumptions: First, Weismann’s particular theory of the 
ultimate structure of the germ-plasm, namely, the theory of 
biophors and determinants; and secondly, the assumption. 
that there is a struggle for food among the determinants. 
There is no proof of pure observation or experiment for 
the theory, and there is some proof directly against it. And 
yet the great need of a working hypothesis for the causo- 
mechanical explanation of determinate variation makes us 
give such a pure speculation more attention than it might 
otherwise get. Unfortunately the attention thus given to 
this particular theory seems to have resulted in the bringing 
forward of some rather serious objections to the possibility 


200 DARWINISM TO-DAY. 


of the truth of the theory. A few of these objections ° may 
be briefly stated. 

According to the theory there should be plainly exhibited 
in the variation of any species, decided tendencies in certain 

Objections to Specific directions. In all species, in all indi- 
eA es a viduals, the struggle of the determinants must 
tion, result in the suppression or reduction of some, 
the extra-development of others. Thus variation should 
not reveal itself according to the law of error, that is, should 
not be distributed normally about a mean or mode. But 
that is exactly the condition of variation in a majority of 
those cases in which the variation of one or more organs 
in any species has been statistically studied. The plotted 
curve of any particular variation of this type is a symmetri- 
cal curve nearly coincident with the theoretical one express- 
ing the law of error for the same case. 

The constancy of species is just as marked and actual a 
condition as the condition of slight fluctuating variations 
inside the species. This constancy is steadfast for con- 
siderable time-periods. But with such an active orthogene- 
sis as the theory of germinal selection provides, there could 
be no such steadfast constancy. Weismann himself recog- 
nised the weight of this objection to the theory, and speaks 
of an attribute of “self-correction”’ pertaining to the germ- 
plasm, which shall regulate or check too rapid an ortho- 
genetic development. | 

The actual change of the competitive determines due 
to their obtaining an over or under supply of food should 
be one simply quantitative in degree; such germinal selec- 
tion could thus lead to the change in size and strength of 
organs already present in the species, but could offer no 
explanation of qualitative changes, 7. e., the appearance of 
new kinds of structures. Moreover, even in cases of purely 
quantitative change, such familiar cases as the persistence 
through long time-periods of small, rudimentary organs, 


OTHER -THEORIES* OF SPECIES-FORMING, 208 


without any indication of further reduction, indicate a pecu- 
liar cessation in the forthright working of germinal selec- 
tion. Why should not the weak determinants of these weak 
organs go completely to ground in the struggle? 

Actual experimentation on the influence of food-supply 
in development does not bear out the assumption on which 
the theory of germinal selection rests. Weismann himself 
gave the larve of flies, and I have given the larve of silk- 
worms through their whole life-time, an abnormally small 
food supply (in the case of the silkworms this supply was: 
from one-fourth to one-eighth the amount normally eaten 
by full-fed larve), with the only result that the mature 
individuals were dwarfed; that all their parts were reduced 
in size, but the actual size proportions of the various organs 
and parts, and their relations to each other, were unchanged. 
The determinants seemed to share equally the hardships of 
short rations rather than a few of the stronger getting the 
better of the weaker. From the eggs of birds considerable 


quantities of yolk have been withdrawn without modifying 


appreciably the individuals developed from the eggs. 

If the struggle of the determinants is really an actual and 
severe one then only those of the large strong organs should 
survive, all the others being starved out. Such a condition 
would result in the exclusive development of monsters, 1. ¢., 
individuals lacking numerous organs (the small ones), and 
with the large ones all over-developed. 

Roux’s Theory of Intra-selection or the Battle of the 
Parts.—Distinctly more likely to appeal to our reason is the 
theory of Roux,’ proposed in 1881, to explain how one or 
more organs may exhibit a progressive development or 
increase in size and capacity without reference to natural 
selection and also to account for the many remarkable adap- 
tations of slight and delicate but extremely precise character 
exhibited by various internal organs. Roux made, however, 
a too radical distinction between external or superficial 


a 


202 DARWINISM TO-DAY. 


adaptations on the one hand, attributing these to the influ- 
ence of natural selection, and the adaptations of internal 
parts on the other, which he would attribute to the influ- 
ence of his functional stimuli and of his struggle among 
the inner parts of the body. This struggle, like that among 
Weismann’s hypothetical determinants, is one chiefly for 
food, but in Roux’s theory there is no assumption of hypo- 
thetical life units, nor any lack of clearness concerning the 
initiation of the actual struggle. The competing parts in 
Roux’s theory are the chemical molecules composing the 

ne eontvetiar cell, the cells themselves, groups or tissues of 
parts in Roux’s cells, and even whole organs. The spurs to the 
theory are actu- re : : : 
ally recognised COMpetition for food are functional stimuli, 
structures. whose result is to set up a special demand and 
necessity for more food. Rouwux’s classic example will make 
this clear. It is a matter of fact that the fine plates and 
layers of bone in the “spongy tissue” of the long bones of 
the body, are so disposed as actually best to withstand the 
stresses most usually brought to bear on the bones. Thus 
they show a fine adaptation of arrangement, which one meets 
difficulties in trying to explain as due to natural selection. 
For, if we imagine the thin plates of the spongy tissue 
purely miscellaneously arranged, the possible slight varia- 
tions whereby a few plates at a time might fortuitously 
occur in a position or direction better fit to strengthen the 
whole bone, are so insignificant in proportion to the condi- 
tion throughout all the rest of the bone that we cannot possi- 
bly attribute to them a life-and-death value in the individual’s 
struggle for existence. Roux assumes that the stresses 
brought to bear on the bone during its development act as 
functional stimuli to all those plates in the forming spongy 
tissue, which lie in such places or at such an angle to the 
stress as to be affected by them, and in response to these 
stimuli, which in Roux’s belief are necessary to the normal 
structural development and maintenance of any part, these 


OTHER THEORIES OF SPECIES-FORMING., 203 


forming bony plates will take up more food than the un- 
stimulated ones, and thus will be developed at 
the expense of these others. Similarly with 
all those other marvellously delicate inner adap- 
tations of fine and minute and oft-repeated structures to the 
special functions of the organs containing these structures. 
The stimulus of the function excites a trophic demand on 
the part of the struggle and an actual capacity for satisfying 
the demand, that soon leads to the extra-development of 
the stimulated parts at the expense of adjacent similar parts 
deriving food from the supply common to all. Thus Roux 
would explain the exquisite adaptation of the arrange- 
ment of the muscle-fibres in the walls of the blood-vessels, 
the tenidia or spiral threads in the trachez of insects, the 
little barbs on the feathers of birds which hold these feathers 
together in almost air-tight continuity, the numerous protect- 
ive hairs covering the spiracles of many insects, etc., etc. 

It will be noted that the competition of the parts is really 
twofold; thus, while for successful development it is neces- 

TEs sary for parts to be successful in food-getting, 
of the partsis this success in food-getting seems to depend 
twofold. upon the prerequisite of receiving a needed 
functional stimulus. Thus there may be said to exist a com- 
petition for functional stimuli. But obviously success in 
this competition depends chiefly on the hazard of position. 
Those plates in the forming -spongy tissue of a long bone 
which happen to lie where the stress comes, and in a special 
direction to be affected by it, are the winners in the compe- 
tition for stimuli. 

Roux’s theory has appealed strongly to many biologists, 
but others have rejected it wholly, or at least as an explana- 

_, tion of fine inner adaptations. Plate takes this 

Plate’s criti- oe . Ble 
cism of Roux’s latter position, but finds a great service in the 
theory. theory in that “Roux has given in it a profound 
analysis of the well-known fact that use strengthens and 


7 


The struggle 
is for food. 


204 DARWINISM TO-DAY. 


disuse weakens. His is the great merit of having clearly 
explained the extraordinary importance (Tragweite), in the 
building of new forms and adaptive structures, of this ele- 
mentary attribute of organisms. We have to thank him for 
the best putting together of all those observations which 
permit of but the one conclusion, that the functional stimuli 
exercise a trophic activity, that is, that each organ by the 
constant exercise of its function becomes stimulated to 
stronger assimilation and increased multiplication of its 
elementary parts, and that out of this there results a height- 
ened functional capacity.”” However, as Plate points out, 
Thelawof this “law of functional adaptation” does not 
functional adap- apply to all organs and tissues; “‘the teeth of 
tation does not : , 
apply to all many mammals become impaired through con- 
aaa stant use, and most of the sense-organs are 
apparently not bettered through use in regard to their per- 
ceiving elements but only in regard to their carrying ele- 
ments. Every exercise is followed by a certain fatigue 
which, in cases of exhaustion, is greater than the aimed at 
(ersielte) increase of functional capacity. Also the trophic 
stimulation can, in certain cases, lead to hypertrophy and 
other unadaptive results.” But as regards the actual “strug- 
gle of the parts,’ and especially as regards the claim that 
such a struggle is to account for inner adaptations, Plate, as 
a consistent natural selectionist, is wholly sceptical. He 
offers five objections to any usurpation of the functions of 
natural selection by this intra-selection theory. First, he 
holds, with Wolff, that it is impossible to place the inner 
adaptations in any sharp contrast with outer adaptations. 
They are contrasted only in that the former stand in a more 
indirect relation to the conditions of life. Indeed a single 
organ, as a claw for example, can show an external adaptive- 
ness in that it might be especially well arranged to scratch 
hard dry ground, and at the same time be distinctly adap- 
tively constructed as regards its fine inner structure. “If 


OTHER THEORIES OF SPECIES-FORMING. 205 


natural selection,’ says Plate, “is capable of producing outer 
adaptations such as making the fur of a mammal thicker 
and thicker as a protection against the cold, why can it not 
increase, or if advantage lies the other way, decrease, the 
number of bony plates in the spongy tissue of the long 
bones ?” 

Second, the capacity of living substance to be stimulated 
to increased food-getting is an elementary attribute of organ- 

TPophio etinra: isms just as the capacities to assimilate, to be 
lation notex- irritable, and to breathe are. This special 
pitted: capacity is not explained by the theory of intra- 
selection; it is, indeed, just now wholly inexplicable. One 
might perhaps fairly assume that it is the result of a gradual 
development from the Protozoa onward, through the influ- 
ence of individual selection. But this is no explanation of its 
origin. Roux, himself, indeed, expressly declares that he 
bases his theory on the proved but not explained fact of 
functional adaptiveness, but some of his followers often 
forget this and seem to claim that the distinctly advantage- 
ous peculiarity of most tissues to be able to increase in 
strength and size through use is a direct result of the 
battle of the parts. 

Third, Plate holds that the battle of the parts plays no 
role in ontogeny. The cleavage and embryonal develop- 

Pore ammentiate wholly controlled by heredity, so that 
parts not evident there is nothing left for the battle of the parts. 
imontogeny. There occurs a peaceful and regular split- 
ting apart of the single cells and a separation of them 
according to their different qualities, and it does not at all 
occur that the strongest cells get all the food and the weak- 
est none, but on the contrary each receives as much as it 
needs for its growth. In a blastula of thirty-two cells it is 
not the capacity on the part of certain cells. which results in 
the stronger growth of some and the weaker growth of 
others, or the more rapid multiplication of some and the 


206 DARWINISM TO-DAY. 


less rapid of others, but, on the contrary, for each species 
there is a definite law of growth which we may only explain 
as the expression of a force of heredity, not capable yet of 
analysis. Matters certainly do not go on in an embryo as 
in an agar culture containing several kinds of bacteria of 
which only that one with the greatest life force remains. 
Were the development of the embryo determined by the 
food-zeal of the cleavage cells, it would happen that in a 
short time a few cells specially capable of assimilation would 
get the upper hand, and as a consequence only a few qualli- 
ties be left to the embryo; a real differentiation into thou- 
sands of different cell-sorts would not be possible. All the 
facts of symmetry and auto-regulation in embryonic develop- 
ment speak against any considerable influence of a battle of 
the parts during development. 
Fourth, Plate declares that in the acquirement of new 
characters no selective intra-struggle takes place, or at least 
in only most insignificant manner, but that the 
iets new structures arise either through the direct 
acquirement of influence of new stimuli or by natural selection 
new characters, . LR ye 
of new germinal variations of unknown origin. 
In the first place it is simply the matter of position, not at 
all that of quality, that decides whether the certain ceils 
shall be changed or not. Think, for example, of a vessel 
in whose walls the connective tissue fibres cross and recross 
in all directions wholly without order, and conceive that a 
constant or repeated stress in both longitudinal and trans- 
verse directions is exerted on this vessel. It would result 
that all those fibres lying in the absolute or approximate 
directions of these stresses would be most stretched and 
would in consequence of their trophic irritability most rapidly 
enlarge and increase with special rapidity. Now by the 
repetition and inheritance of this result of use it would finally 
come about in the course of generations that all the fibres 
situated in other directions to the stresses would die out, 


OTR E RP LAE ORIBS Ob SireCino-hORMING, 207 


and thus a definite longitudinal and transverse arrangement 
of fibres in the walls of the vessel result. Without doubt, 
holds Plate, much advance is won in this way, but this 
specialisation of structure is not a result of intra-strugegle 
but rests on the elementary attribute of trophic irritability. 
Not the best-qualified but the best-situated fibres have van- 
quished the others by robbing them of food and thus finally 


destroying them. In the second place, “many inner struc- My 


tures belong to the great category of passive adaptations; | 


they function only through their presence and cannot thus || 


be further developed by use or disuse, that is, by functional 
stimuli, but only by natural selection. Here belong, for 
example, the stratification of the lens in the human eye, the 
apodemes (inner projections of the chitinised cuticula) 
which protect the ventral nerve-cord of the crabs, the chitin 
hooks which hold together the fore and hind wings of many 
insects, and the similar structures which bind together the 
secondary branches of the feather vanes of birds. These 
inner adaptations cannot have resulted through the influence 
of light or of nervous function or flight. There is but one 
explanation possible; namely, that natural selection has 
seized on and developed fortuitously appearing germinal 


variations. But if natural selection can produce such inner /, 


adaptations why can it not then produce all the others?” 
Fifth, Plate points out that Roux’s theory is based on the 
inheritance of those special body characters which are 
meant acquired through the battle of the parts—more 
Rour'stheory Tightly, Plate holds, through functional adapta- 
baer edie ng tion,—so that to accept the theory, one has to 
acquired char- declare, to that degree, a belief in the inherit- 
ee ance of acquired characters. Thus from the 
start, the neo-Darwinians cannot accept the theory. . 
After all what is this theory of Roux’s but a refinement, a 
special case, of the broader and more general long-known 
Lamarckian theory of the modifying and formative influ- 


208 DARWINISM TO-DAY. 


ence of use and disuse, accumulated through inheritance? 
That is, if we accept Plate’s analysis that the theory 1s 
really not one of a battle of the parts, but of 
The battle of ; : ; 
the parts theory the effects of functional stimuli. And however 
poeta ah the proposer of the theory may protest against 
such an apparent violent setting over of it from 
the category of selection (Darwinian) theories into that of 
the inheritance of use (Lamarckian) theories, I believe that 
most of us will see the justness of Plate’s analysis. I do 
not believe that Roux’s theory in any way strengthens the 
selection conception. To my mind, indeed, it is simply a 
concession of the inadequacy of selection to initiate adapta- 
tion, and a welcome and satisfying explanation of how such 
an initiation may occur in many cases, in certain cases, that 
is, of active adaptations. Plate’s argument that natural 
selection must be the only explanation for the cases of 
passive adaptations and hence may be held capable for 
accounting for the active ones, has no conviction for me, for 
I do not believe that natural selection is the only possible 
explanation of the passive cases. In fact, I cannot conceive 
it to be a possible explanation of the initiation of these cases. 
And I am glad to find in Roux’s theory—even if it be not 
exactly applied in Roux’s own sense—a mechanical expla- 
nation of the possibility of initiating certain fine and delicate 
inner adaptations. 
/ Organic Selection.—An interesting attempt to escape from 
the difficulties which are imposed on one by an absolute | 
adherence to Weismann’s doctrine of the impos- | 
Organicselec- ., .,. 2 ; ; 
/ tion, orthoplasy, Stbility of the inheritance of acquired characters | 
eames coupled with a belief in the inadequacy of the | 
slight fluctuating germinal variations to afford | 
handles for the action of natural selection, is the theory va- ' 
riously called organic selection, or orthoplasy, proposed by 
Baldwin* and Osborn’ in America, and Lloyd Morgan”? in 
England. This theory, which might also be called one of 





OTHER THEORIES OF -SPECIES-FORMING. 209 


“ontogenetic selection,” or of “coincident selection,” is that 
the personal selection, or individual survival, among indi- 
viduals of a species does not necessarily depend solely upon 
congenital variation but may, must, indeed, depend on any // 
ontogenetically acquired adaptations as well. As in many — 
cases these ontogenetic adaptations are considerable, they 
will often carry individuals through very critical periods in 
their lives. But the individuals showing these ontogenetic 
adaptations in best degree will be those which actually pos- 
sess certain slight congenital variations, especially of the 
nervous system or coordinating nerve centres, “which lend 
themselves to intelligent initiative, adaptive, or mechanical 
modification during the lifetime of the creatures which have 


them.” The ontogenetic adaptations may occur regularly | / 


in the lives of successive generations of individuals if the — 
environment remains fairly constant. During these suc- 
cessive generations the congenital variations of brain, say, 
which make the successful ontogenetic adaptations possible, 
will by selection of the best ontogenetically varying individ- 
uals be themselves selected, and the species thus gradually be 
modified in a determinate direction. Also congenital varia- 
tions of nearly the same nature as the ontogenetic variations, 
or of a nature to supply the same need, will have time (that 
is, more chance, because of the longer time and repeated 
generations) to appear. In this case these advantageous 
variations can be transmitted directly by heredity, and thus 
a permanent adaptation be effected which will seem to be the 
result of the inheritance of an acquired character (i. e¢., the 
similar ontogenetic modifications) but which in reality is 
only the normal inheritance of a congenital variation. 

In the language of all the sponsors for this theory there 
seems to be a suggestion of the piling up or adding together 
of congenital variations, not simply those of brain or other | 
control centre which make the ontogenetic modifications || 
possible, but also of these modifications themselves during the 


wei 


210 DARWINISM TO-DAY. 


successive generations through which the species is safely 
carried by the temporary regularly appearing ontogenetic 
adaptations. But there is nothing in strict neo-Darwinism 
to permit of any such idea of increase. Such moving for- 
ward without the aid of selection can only be explained by 
the adoption of some theory of orthogenesis. Either the con- 
genital variations are of such a character that the resulting 
ontogenetic modifications are not fairly to be distinguished 
from them, in which case they are assumed to be large 
enough from the start to afford handles for natural selection 


, (which the proposers of the theory are not claiming), or 
‘ they depend for their preservation on a kind of happy coinci- 


dence in occurrence with similar more effective ontogenetic 
modifications which are really large enough to save the life 
of the organism and hence the slight congenital variations 
along the same line. But in this latter case organic selection 
cannot demand much discussion until it explains away a 
Delageand radical failing pointed out clearly by Delage 
ena, and Plate. This is simply that, in the face of} 
tion, the large character which ontogenetic adapta- 
tion may and often does possess, those individuals in which | 
the slight congenital variations in the right direction finally 
appear will have no special advantage over those in which 
they do not appear; the large and effective character of the 
ontogenetic adaptations, which are common to both kinds of 
individuals, being quite sufficient to determine the result of 
personal selection. The congenital variations will be too 
small in comparison with the ontogenetic variations to cut 
any figure in the fate of the individuals, and there is no 
reason at all to believe that individuals showing the slight 
congenital variations in the right direction will be the only 
ones to show the saving large ontogenetic adaptations. 
Plate suggests the following case to show the inutility of 
this theory : Suppose an antelope species to have a leg muscle 
averaging seven cm. in thickness, and several individuals to: 


I 


OTHER THEORIES OF SPECIES-FORMING. 211 


show a congenital variation bringing the leg muscle up to 
eight cm. of thickness. Now if it requires a leg muscle of 
eight cm. for safety, as a matter of fact almost all the indi- 
viduals of the species will quickly bring their leg muscles up 
to that size by use. But suppose the actual need for safety 
was a leg muscle of fourteen cm., then only those individuals 
specially capable of that ontogenetic adaptation, 1. e. (modi- 
fication of the leg muscle by use and trophic irritability), up 
to fourteen cm., would be saved; and undoubtedly among 
these the original eight cm. individuals ought to stand in 
slightly higher numerical proportion (in regard to their 
original numerical standing in the species) than the origi- 
nally seven cm. individuals. Since, however, these eight cm. 
individuals originally existed only in comparatively small 
number, and since they possess no special means of recognis- 
ing each other and distinguishing each other from the 
original seven cm. individuals, mixed mating will inevitably 
soon swamp the original congenital increase of one cm. in 
muscle thickness. 

In connection with the explanation of this theory it will 
certainly occur to some of my readers, as it has to me, to ask 

Danek if it is not a dangerous proposal to give to 
assuming too ontogenetic adaptations a greater worth in 
great 1mport- has sug ein. « : 
aes efontos. wn aeciainag the) fateyof individuals ‘during: the 
genetic selection. stryeole for existence than the congenital varia- 
tions. Is this not proposing to take away from the fluctuat- 
ing, individiual, so-called Darwinian variations practically 
all worth and capacity except as they are of immediate use 
to the just-born individuals, 7. e., before the ontogenetic 
adaptations have been able to develop? Indeed, why is it not 
a perfectly legitimate and a serious criticism of congenital 
fluctuating variations that they must be overshadowed, hid- 
den, and overwhelmed by the quick and large ontogenetic 
or individual modification of which practically all organisms 
are capable? Why will not those individuals born with the 


ie DARWINISM TO-DAY. 


better and larger capacity to adapt themselves during their 
ontogeny to their needs win in the struggle for existence 
rather than those born with predetermined slightly larger 
leg, slightly stronger muscle, etc.? What is needed is 
capacity to develop by use and functional stimulus a much 
stronger muscle, a much swifter flight than the average. 
Those individuals that are capable of such considerable and 
really worth while ontogenetic adaptation will win in the 
struggle for existence; and while they may not hand down 
by inheritance their actually acquired characters, will they 
not hand down their inherited congenital capacity for con- 
siderable and effective ontogenetic adaptation? 


APPENDIX. 


* For a fairly complete bibliography, with abstracts, of all the 
important discussions of species-forming theories published since 
1895, see L’Année Biologique (ed. Y. Delage). For bibliography 
and abstracts, also see Zoologischer Jahresbericht, issued annually 
by the Naples Zoological Station. See also discussions and notes 
in various biological journals, as Biologisches Centralblatt, Natural 
Science (now discontinued), Nature, Science, American Naturalist, 
etc. 

* For a careful account and discussion of Weismann’s work and 
theories as far as developed up to 1893, see Romanes, “An Exami- 

List of Weise mation of Weismannism,” 1803. Weismann’s pres- 
mann’s evolution ent-day position and his arguments for the selection 
Papers: theories are set out in his ‘‘Vortrage tiber die De- 
scendenztheorie,” 2 vols., 1902, which we may look on as consti- 
tuting a manual of neo-Darwinism, treating all the more familiar 
bionomic phenomena and conditions as explained by selection. 
The following is a chronological list of the more important of 
Weismann’s publications : 

“Uber die Berechtigung der Darwin’schen Theorie,” 1868. 

“Uber den Einfluss der Isolirung auf die Artbildung,” 1872. 

“Studien zur Descendenztheorie: I, Uber den Saison- Dimorphis- 

. mus der Schmetterlinge,” 1875. 

“Uber die Dauer des Lebens,” 1882. 

“Uber die Vererbung,” 1883. 


OTHER THEORIES OF SPECIES-FORMING, oh ts 3 


“Uber Leben und Tod,” 1884. 
“Die Continuitat des Keimplasmas als Grundlage einer Theorie 
der Vererbung,” 1885. 

“Uber den Ruckschritt in der Natur,” 1886. 

“Uber die Bedeutung der Sexuellen Fortpflanzung fir die Selec- 
tionstheorie,’ 1887. 

“Uber die Zahl der Richtungskérper und iiber ihre Bedeutung 
fiir die Vererbung,” 1887. 

“Botanische Beweise fiir eine Vererbung erworbener Eigenschaf- 

eter, CIs, 

“Uber die Hypothese einer Vererbung von Verletzungen,” 1880. 

“Bemerkungen zu einigen Tages Probleme,” 1890. 

“Gedanken tber Musik bei Tieren und beim Menschen,” 1890. 

“Aufsatze uber Vererbung und verwandte Biologie,” 1892. (This 
includes the eleven preceding papers now. published in book- 
form. These essays have also been translated into French, 
by H. de Varigny, and published under the title: ““Essais sur 
lHérédité et la Sélection Naturelle,” 1892; and also in Eng- 
lish as “Essays upon Heredity and Kindred Biological Prob- 
lems,” trans. and ed. by Poulton, Shoneland, and Shipley, 2 
vols., 1891 and 1893. 

“Amphimixis oder die Vermischung der Individuen,” 1891. 

“Das Keimplasma; eine Theorie der Vererbung,’ 1892; Eng. 
trans., by Parker and Ronnfeldt, as “The Germ-plasm; a 
Theory of Heredity,” 1893. 

“Die Allmacht der Naturztichtung, eine Erwiderung an H. Spen- 
cer,” 1893; also in English as “The All-sufficiency of Natural 
Selection,” in the Contemp. Review, Vol. LXIV, pp. 309-338, 
596-610, 1893. 

“The Effects of External Influences upon Development,” Romanes 
Lectures, 1894; also in German as “Aussere Einfltisse als 
Entwicklungsreize,” 1894. 

“Neue Gedanken zur Vererbungsfrage,” 1894. 

“Uber Germinal-Selection,” in Compt. Rendus, 3d Congress In- 
ternat. Zool., 1896; also, in English, trans. and ed. by Mc- 
Cormack, as “On Germinal Selection as a Source of Definite 
Variation,” 1806. 

“Thatsachen u. Auslegungen in Bezug auf Regeneration,” Anat. 
Anzeig., Vol. XV, 1899. 

“Vortrage uber Descendenztheorie,” 2 vols., 1902; also in Eng,, 
trans. by J. A‘ Thomson as “Lectures on the Theory of 
Descent,” 2 vols., 1904. 

* For a detailed critical discussion of panmixia, see Wolff, “Der 

gegenwartige Stand des Darwinismus,”’ 1896. 


214 DARWINISM TO-DAY. 


* Various theories of ultimate protoplasmic structure have been 
proposed to explain what is not really known about this substance. 

Theoriesoful- hese theories refer almost exclusively to the physi- 
timate protoplas- cal, rather than the chemical, make-up of protoplasm, 
mic structures and for the most part have been proposed with 
special attention to the germ-plasm, 7. e., the protoplasm of the sperm- 
and egg-cells. The spur to the formation of these theories is the 
necessity that biologists have felt imposed on them from the be- 
ginning of the study of heredity and development of offering some 
rational explanation of those phenomena. That from a single germ- 
cell formed by the fusion of a sperm-cell and an egg-cell from 
different parents, a complete new organism composed of millions 
of cells of manifold variety of specialisation and arrangement can 
develop, is wonder enough; but that this new organism shall repeat 
in all its parts with extraordinary fidelity the structure and physi- 
cal idiosyncrasies of one, or show a combination of the character- 
istics of both, of the individuals from which came the original 
single sperm- and single egg-cell, adds wonder to wonder. What 
physical or structural basis is there in the fertilised egg-cell that it 
can represent in its tiny self the whole of a giant body, like that of 
an elephant, whose every detail it can, by a process of development 
under suitable extrinsic conditions of temperature, food-supply, etc., 
repeat in a new creature. The answers to this, all purely specula- 
tive, or more fairly theoretical, because some of the answers at 
least have been guarded in their forming by all the care which a 
rigorous scientific attitude toward hypothesis demands, are many 
and various, and date from the days of the Greek philosophers to 
the present hour. It would take too much space and carry us too 
far afield to attempt anything like an explanatory list of even all 
of the better known of these general theories of the invisible ulti- 
mate structure of the germ-plasm here, but by selecting seven or 
eight types of the principal categories or kinds of these theories, 
and briefly explaining them, we may have at least some conception 
of the attitude that biologists take toward this great problem. The 
reader who has a fancy for following this subject further is re- 
ferred to the admirably full and lucid treatment of it in Delage’s 
great work, “L’Hérédité” (2d ed., pp. 431-772, 1903). 

Most of these theories include much more in them than a simple 
speculation as to the ultimate structure of the life-substance; they 
attempt to explain all the phenomena of life, motion, nutrition, 
growth, reproduction, development, heredity, variation, etc., with 
reference to some assumed ultimate make-up of the primitive life- 
substance, and the relation of this structure to the known physico- 
chemical forces and conditions of Nature. Most of the older 


OTHER THEORIES OF SPECIES-FORMING. 215 


theories assumed a peculiar vital force, which is not assumed in 
the later ones, although exception must be made to this statement in 
favour of the point of view held by the recent so-called neo-Vitalists, 
those present-day workers who admit the hopelessness of trying to 
reduce all vital phenomena to a physico-chemical basis. 

An old type of theory of heredity and structure of the germ- 
plasm, widely held in the seventeenth and eighteenth centuries, is 

Encasement that of the “encasement of the germ” in one of the 
theory, germ-cells, either the spermatozoid or the egg. The 
essential part of this theory is that the new organism is assumed 
actually to exist in miniature, with all its parts present, in one of the 
germ-cells, and in this miniature body must exist, by repeated encase- 
ment, all its future progeny. Whether the believer in this theory con- 
sidered the tiny new creature, only needing to swell and grow to be 
complete, to be encased in the sperm-cell or the egg-cell, ranked 
him respectively with the spermatists or the ovalists. A vigorous 
strife raged between these two factions among the upholders of 
this simple and effective explanation of heredity which led to cer- 
tain interesting compromises. A commonly held one was that the 
sperm-cell furnished the spiritual element, the egg-cell the material 
and mechanical elements of the new creature. Another, held by 
Linnezus, the great botanist and father of biological classification, 
was that, in plants, the egg (ovule) furnished the internal and re- 
productive organs, while the sperm-cell (pollen) furnished the exter- 
nal and vegetative parts. De Candolle, another great botanist, held 
just the reverse of this view. All these theories of an actual 
encasement in the germ-cells of a whole or part of a new organism 
were not mere guesses, but were based on what men thought they 
saw through their microscopes. The long reign of these theories, 
now shown to be utterly absurd, illustrates well the constant dan- 
ger which attends our attempts in all biological study to interpret 
what we see when working at the limits of visibility. With our 
much-improved microscopes we laugh at the fantasies which the 
microscopic vision of our eighteenth-century co-workers raised up. 
Who may say that our own interpretations of plasm-structure may 
not seem as absurd to the biologists of the next century? 

By far the great majority of theories of ultimate protoplasmic 
structure belong to what Delage calls the category of theories of 

Micromeric micromerism. Which means simply that all these 
theories. theories assume a composition of the plasm out of 
minute ultra-microscopic units of structure, which are also units 
of life, for all these units are presumed to be endowed with the 
essential life-attributes. These units may be looked on, as they 
were by Buffon, as universal, indestructible, hence immortal, parti- 


216 DARWINISM TO-DAY. 


cles, or, as they are in most of the micromeric theories, as living 
particles. which are destroyed with. the death of the organism 
which they compose. In this latter type of assumption the units 
are, according to some theories, all of the same nature, all exer- 
cising an equal influence in determining the character of a devel- 
oping organism (Spencer, Haacke, His, Cope); or they are, as 
assumed in other theories, of various character and charged with 
various functions. This latter kind of unit is held by some authors 
to be actually representative either of ancestral plasmas (Weismann) 
or of the actual body-cells of the parent (Darwin, Galton, Brooks, 
Hallez), or of elementary characteristics and functions of the 
organism (Nageli, Kolliker, de Vries, O. Hertwig), or at the same 
time of both body-parts and elementary characteristics (Weismann’s 
latest theory). 

Buffon’s theory assumed that “the substance of which organisms 
are composed differs essentially from that which composes the 

Buffon’s inorganic bodies. Organisms are composed of special 
theory. particles, the organic molecules. These molecules are 
universal and indestructible: universal in that they exist everywhere 
where life has access, indestructible in that death and the dissolution 
which follows destroy the organisms, break down the molecular com- 
binations which constitute them, but do not reach the molecules 
themselves. These are only separated, put at liberty, but remain 
ready to enter into new groupings. While they cannot be de- 
stroyed, neither do they increase in numbers. They form nothing 
actually new, either spontaneously, or by means of old ones, so 
that, measured by these organic molecules, the total quantity of life 
in the universe is invariable’ (Delage). Nearly a hundred years 
later Bechamp (1883) proposed a theory similar to Buffon’s in 
which he assumed the composition of organisms out of minute 
elementary living particles called muicrozymes. Like Buffon’s 
organic molecules they are indestructible, and they are strewed in 
innumerable numbers through earth, air, and water. They owe their 
origin to special creation by God. 

Of the non-immortal kind of micromeres Spencer’s physiological 
units represent a general type favoured by numerous theorists: 
namely, living units all of the same nature and active because of 
their polarity, their form and molecular forces, or their vibratory 
motion. Spencer’s physiological units are active because of their 
polarity, but the annular atoms of Dolbear’s theory and the 
plastidules of the slightly varying theories of Haeckel, His, Cope, 
and others, owe their active properties to their vibratory motion. 

According to Spencer (1864), there exist between the cells 
(morphological life-units) and the molecules which compose them 


OTHER THEORIES: OF ‘SPECIES-FORMING, 21% 


(chemical units), units of a third order (physiological units) com- 
Spencer's posed of groups of molecules. These units are very 
theory. small but very complex, and are the smallest masses in 
which living substance can occur. Most of the micromeric theories, 
which come after Spencer’s, adopt this conception of a life-unit, very 
‘small, but composed of an aggregate of molecules, and therefore 
very complex. To his physiological units Spencer attributed a 
polarity, wholly analogous with that possessed by the molecules 
of crystalline substances. It is owing to this delicate, precise 
polarity, varying of course with the varying molecular consti- 
tution of the units, that they possess the capacity of actively 
arranging themselves in the varied groupings normal to the parts. 
of the organisms. “Thus the resemblance is perfect between the 
chemical polarity which causes crystallisation and that of the 
physiological units which produces the form of organisms. In one 
case the chemical molecules group themselves in a manner to form 
an aggregate of definite but simple form, cubical, prismatic, 
rhomboidal, with their parts arranged en tremites, aiguilles, croix 
de Saint André, boules épineuses, etc. In the other the units group 
themselves in a body of a form less rigorously defined but which 
may be very complicated: such as a plant or an animal.” (Delage.) 
Of the theories in which the living units are assumed to be of 
different kinds, and endowed with different functions, some assume 
the units to be not directly representative of different cells or parts — 
of the body, while others assume this truly representative condition. 
Of the first sort are a number of theories like those of Berthold, 
Geddes, and others, in which the units are taken to be actual 
chemical molecules, endowed with activity through special physico- 
chemical properties or through purely chemical ones, while still 
others keep to the more usual type of a unit of a higher order 
than a molecule, in which case also this unit is looked on as spe- 
cially active because of particular electrical (Fol) or chemical 
(Altmann and Maggi) or vital (Wiesner) endowment. But all of 
these theories are much like each other and are much like Spencer’s 
theory in regard at least to the assumed units. Different, how- 
ever, is the type of theory which introduces the assumption that 
the fundamental life-units are directly representative of either 
the specific cells, parts, or elementary characteristics of the organ- 
ism. This is the kind of unit especially favoured by the men 
who had, in their formation of a theory, a special eye to the 
problem of heredity. How is the single germ-cell to be the bearer 
of the “heredity” of the organism from which it comes? what 
more simple to assume than that this cell shall be composed of 
minute particles gathered from all the cells or groups of similar 


218 DARWINISM TO-DAY. 


‘cells of the body of the parent? And that is precisely the charac- 
teristic assumption, dressed up in an ingenious variety of form, 
which characierises the theories of life-units most favoured at 
present: such theories are those of Darwin, Galton, Brooks, Nageli, 
de Vries, Hertwig, and Weismann. In some of these, interesting 
attempts are introduced to connect the assumed structure with 
the actually observed finer structure of the nuclear protoplasm, by 
introducing combinations of the fundamental units, in one or two, 
or even three, successive degrees until an aggregation is reached 
which corresponds with those microscopic structures, the chromo- 
somes, or chromatin granules or threads, which are actually visible 
to the microscope-aided eye. The most recent one of the theories 
of this general type is that of Weismann’s biophors and determi- 
nants structure of the germ-plasm, already explained in connection 
with the presentation of his theory of germinal selection (see pp. 
193 ff.). As other examples we may note especially Darwin’s, 
called the theory of the pangenesis of gemmules; and Nageli’s, 
called the theory of micelle and idioplasm. 

Darwin’s gemmules are extremely minute particles, which are 
formed in all the various cells of the body and are capable of repro- 

Darwin's ducing themselves rapidly and in great numbers by 
theory. repeated division, and which, by virtue of their minute 
size and an innate activity due to a sort of affinity or attraction exist- 
ing between them and other substances, move about freely in the body, 
penetrating any membranes, and arranging themselves with a deli- 
cate precision just where they are most needed. When a gemmule 
enters an undifferentiated or developing cell as yet containing no 
other gemmules, it controls the development of that cell so that it 
becomes a cell of the type from which the gemmule had birth, each 
gemmule representing thus exactly the characteristics and the type 
of its mother cell. Thanks to the delicate and precise adjustment 
of affinities, migrating gemmules only enter those cells which they 
really should enter in order that a normal development of all the 
cells of the body should go on. But those few cells of the body 
which are destined to become germ-cells, that is the spermatozoids 
and eggs in animals, the pollen grains and ovules in plants, receive 
during their formation gemmules from all the other cells of the 
body. Not only from all the cells of the fully developed body, but 
from all those ephemeral cells which arise and live for a while 
during the ontogeny of the parent, performing certain special func- 
tions and then making way for the definitive cells of the mature 
organism. Thus in the germ-cells are stored actual physical repre- 
sentatives of all the cells which have existed during the whole life 
of the parent body. These innumerable gemmules remain inactive 


OTHER THEORIES OF  SPECIES-FORMING. 219 


in the germ-cells until, after fertilisation, the egg-cell begins its 
development. Then as the cells of the new organism begin to be 
produced, the gemmules become active and each one moves into 
the cell it should control and there directs its further development 
into precisely the kind of cell it should be at precisely the time it 
should be this kind of cell, until there results from this gemmule- 
controlled development a photographic reproduction of the parent 
body. 

Nageli’s conception is that when the complex life-characterising al- 
buminous substances took their birth in an aqueous liquid, they would 

Nageli’s be precipitated, as they are not soluble in water. This 
theory. precipitate is formed of small masses, a sort of organic 
crystals, which may be called micelle. And just as an inorganic 
crystal deposited in a saturated saline solution of the same nature 
determines the deposit on its surface of the dissolved molecules in 
the form of little crystals, and by this means grows, so wherever 
any micelle are formed they facilitate within their sphere of influ- 
ence the precipitation of others, so that this production of micellz 
instead of taking place miscellaneously through the liquid will be 
localised at certain points. Thus arise aggregates of albuminous 
substance, in the condition of micelle, forming the primitive 
protoplasm. The micellz, although insoluble in water, have a great 
affinity for it, and each one at the time of its precipitation fixes 
around itself a thin layer of water, at least as thick as a water 
molecule. Thus, all the micelle grouped together in a bit of primi- 
tive protoplasm are separated from each other, and also held to- 
gether by a layer of water as thick as two water molecules. This 
water forms an integral part of the protoplasm. By virtue of it, an 
aggregate of albuminous micellz can increase by intercalcation as 
well as by the addition of new micellz on the outer surface. By 
admitting more or less water the protoplasmic mass may become 
more or less nearly fluid. Thus are accounted for the various 
densities always met with in the different parts of a protoplasmic 
cell. 

A further essential part of Nageli’s theory is an arrangement of 
the primitive protoplasm in two’ ways, resulting in two kinds of it, 
which are called nutritive plasm and idioplasm respectively. This 
arrangement depends on the molecular forces pertaining to the 
micelle, and the difference, resulting in two kinds of plasm, depends 
upon the relative situation of the micelle composing the mass, just 
how this affects them differently, however, not being made very clear. 
But the differentiation is very important, for it is the idioplasm 
alone which contains the essential life-properties and which really 
gives rise to life with all its variety and complexity. This idioplasm 


220 DARWINISM TO-DAY. 


is formed at first in scattered bits in the nutritive plasm mass, but 
as these bits increase they join and become united into a network 
surrounded by and containing in its meshes the nutritive plasm. 
And one of the most interesting parts of Nageli’s hypothesis is that 
he conceives this network of idioplasm not to be limited by cell 
boundaries but to penetrate from one cell into adjacent cells and 
thus to spread through and unite in a most significant and important 
way all the cells and tissues of the body. It is just this sort 
of a ramifying, stimulus-carrying, protoplasmic network connect- 
ing all the parts of the body that the believers in the inheritance 
of acquired characters seem to need as a mechanism to transmit 
from soma to germ-cells the effects of external and functional 
stimuli. 

Next, the theory of intra-cellular pangenesis of de Vries may 
be briefly stated. This theory has become the more important be- 
cause of the great interest aroused by and the large appreciation 
given to the mutations theory of species-forming of the same 
biologist. De Vries’s theory of intra-cellular pangenesis has much 
in common with Darwin’s theory of the pangenesis of gemmules, 
but it is able to do away with that particularly weak part of Dar- 
win’s theory, which postulated the circulation of the gemmules 
throughout the organism in order that they should meet in the 
germ-cells and modify these cells in a parallel way with the modi- 
fications occurring in the peripheral organs. Darwin had to postu- 
late this circulation of the gemmules through the organism in order 
to explain the phenomena of regeneration, and the heredity of 
acquired characters. Now that the heredity of acquired characters. 
has been shown to be at best an extremely doubtful phenomenon, 
and that regeneration is explicable by other means, de Vries has 
been able to drop this weakest part of the Darwinian conception. 
So that in the theory of the later biologist, the circulation of gem- 
mules does not extend from one cell to another throughout the 
body of the organism, but limits itself to that particular cell in 
which it is created and circulates only between the nucleus and 
cytoplasm, from which comes the name, “intra-cellular pangenesis,” 
as distinguished from Darwinian pangenesis. De Vries’ theory may 
be abstracted as follows (following Delage) : 

The form and properties of cells result from their protoplasmic 
composition just as the properties of the inorganic bodies result 

De Vries’s from their chemical composition. Is it necessary, then,, 
theory. to admit that there are as many kinds of protoplasm as 
there are different sorts of cells in the organised beings? When one 
recalls how many different cells there are in a single organism, and 
that the homologous cells are not identical in different species, one 


OTHER THEORIES OF SPECIES-FORMING., 221 


realises the incalculable number of these cells and despite the rich- 
ness in variety of proteid substances, it will be impossible to con- 
ceive that each kind of cell should have its own kind of proto- 
plasm. There is here, apparently, an insurmountable difficulty, but 
one which it is easy to do away with by a very simple concep- 
tion. This conception consists in distributing the complex charac- 
ters and properties, innumerable in living beings, into elementary 
characters and properties much less numerous, which, by varying 
combinations, produce the almost infinite variety that we observe 
in the inorganic world. Just as with a score and a half of letters 
one may form all of the words of the human language, so with the 
elementary properties of which the actual number is still very con- 
siderable, one may reproduce all the characters of living beings in 
all their variety and complexity. It suffices, then, to admit that 
these elementary characters and properties are represented by as 
many material particles, and the problem is solved. These particles 
are the pangenes. 

The pangenes, then, are small, organic particles, invisible to 
the microscope, formed of an enormous number of chemical mole- 
cules and differing from the most complex chemical substances 
by three properties which are common to all of them and which 
are characteristic of living matter; they nourish themselves, in- 
crease in size, and multiply themselves by division. Beside these 
three general properties which make living molecules of them, 
the pangenes possess particular properties depending upon their 
chemical constitution, differing for each of them, and which are 
bound to them indissolubly in such a manner that, wherever a 
pangene finds itself, the elementary property or character special to 
it will show itself if internal and external conditions permit of this 
manifestation. Latent or patent, potentially or evidently, the char- 
acter is always there where is the corresponding pangene. Each 
cell contains a great number of pangenes in activity, and its charac- 
ters and properties in sum are the resultant of the elementary 
characters and properties of the pangenes composing it: just as the 
anatomical and physiological characters and properties of the living 
individual are resultant of the anatomical and physiological charac- 
ters of the cells composing it. 

It is necessary to conceive of the cellular protoplasm as formed 
of innumerable pangenes bathed in a liquid in which are dissolved 
substances purely chemical: albumen, glucose, salts, etc. Perhaps 
similar substances penetrate the pangenes themselves, but we do 
not know this. 

The nucleus contains in general all the kinds of pangenes that 
compose the individual. But these pangenes are there in a sort 


E22 DARWINISM TO-DAY. 


of inactivity, in reserve, in order to be transmitted to the daughter 
nucleus when the cell divides. They can divide themselves, and it 
is indeed necessary that this be so in order that the two daughter 
nuclei can each receive a complete lot of the representative pan- 
genes; but they do not manifest in the nucleus their special proper- 
ties, which remain in a latent state. There is no exception to this 
except in the case of those certain pangenes which control the 
division of the nucleus. These enter into activity at the necessary 
moment in order to determine the characters of the division and 
in particular the position of the plane of segmentation. 

The cytoplasm is also composed of pangenes; but these pangenes, 
with the exception of those which come from the cytoplasm of the 
egg, come from the nucleus. From the nucleus there come, in fact, 
pangenes which distribute themselves in the cytoplasm and multiply 
there abundantly. These pangenes are exclusively those of which 
the cytoplasm has need in order to manifest characters and proper- 
ties which belong to the cell, and it is by delivering to it such and 
such pangenes and no others that the nucleus rules the cytoplasm, 
which would remain inert were it not for this infusion of living 
and active particles. 

There is, then, a great difference between the nucleus and the 
cytoplasm from the point of view of the pangenetic constitution. 
Each nucleus contains in general all the pangenes of the individual 
united undoubtedly into groups more or less considerable, which lie 
in the chromatic filaments, and these groups, analogous to the 
gemmules of Darwin’s theory, probably form those little grains 
arranged in rows, which are revealed under a great microscopic 
magnification of the chromatic threads. But there are one, two, or, 
at most, a small number of pangenes of each kind; all are inactive 
save at the moment of division, those which rule this phenomenon ; 
they can multiply themselves but slightly, and in general they do 
not divide except to replace those which emigrate into the cyto- 
plasm and to furnish at the moment of division to each daughter 
nucleus the complete lot which it ought to receive. In the cyto- 
plasm, on the contrary, there is but a small number of kinds of 
pangenes immigrated from the nucleus in the quantity exactly 
necessary, but there these pangenes are enormously multiplying, so 
that there is a very great number of each kind, and they are almost 
always in a state of activity. 

B. Hatschek has recently proposed (““Hypothese der Organischen 
Vererbung,” 1905) a new micromeric theory which postulates that 

Hatschek’s the protoplasm is composed of two different kinds cf 
theory, biomolecules; one called ergatules, which function as- 
similatively, that is, take up food-stuff and excrete waste, but do not 


OTHER THEORIES’ OF SPECIES-FORMING. 22% 


possess a capacity for growth or self-reproduction; second, the gen- 
eratules, which have no particular functional work to perform but can 
grow and reproduce themselves and can carry over this capacity of 
reproduction to the ergatules, because they can fuse with them or 
attach themselves to them and thus carry over to them their char- 
acteristic peculiarities. These generatules are looked on as the 
chemical radical of the ergatules, and become therefore the directly 
determining agents for all peculiarities of the body. The ergatules 
sit chiefly in the cytoplasm of the cell, while the generatules lie in the 
cell nucleus, especially in the chromosomes, and therefore render 
these the bearers of hereditary characteristics. 

Thus baldly and wholly incompletely stated these theories of 
ultimate plasm structure which shall be of a sort to agree with all 
the varied phenomena of life, and particularly those of heredity,,. 
show, unfortunately, only their fantastic face. For as it is pre- 
cisely in showing how the postulated structure and properties are: 
perfectly consonant with all the known phenomena of life that 
these theories have their actual interest and strength, a fantastic 
and improbable face shown as to this robs them of all interest. But,. 
perhaps, it is well that the fantastic aspect of them should be first 
recognised. For it is only fair to say that the ingenuity and plausi- 
bility, the precise and exhaustive development of detail, of some of 
these theories, are really dangerous to the layman who first happens 
to read a full and well-stated account of one of them by an enthu- 
siastic upholder. One’s eyes become closed to the fact that all the 
structure and performance that seem so natural, and fit in so 
exactly with all that we actually know of the phenomena of life, 
have not been seen, only imagined. One needs an introduction to 
these theories which insists above all on their wholly hypothetical 
character. Otherwise one is surprisingly readily hypnotised into 
accepting one or the other of them as a statement of fact. These 
general theories are the atomic theories of biology without one- 
tenth the probability of truth or one-tenth the actual acceptance 
in science that the atomic theory of the chemists has. And even 
that is beginning to be discarded in modern chemistry. These 
theories are, as Weismann has said, the outcome of the fact that 
“the deeper one studies into the phenomena of heredity, the more 
one is convinced that something of this kind of a condition [of a 
composition of the fundamental life substance out of ultra-micro- 
scopic units bearing a certain spatial relation, and one of attractions 
and repulsions to each other] must really exist: for it is impossible 
to explain the observed phenomena in any other way, that is, by 
any much simpler assumption.” But on the other hand a sufficient 
reason against accepting any one of these highly developed theories. 


224 DARWINISM TO-DAY. 


of the structure and functional capacity of invisible life-units, is 
the sagacious one of Delage when he says that simply by the law 

Delage’s of probabilities it will be impossible by pure imagining 
criticisms, to ‘explain correctly in detail the ultimate structure 
of protoplasm. Has any one, asks Delage, guessed in advance, with 
the least truth, structures which the microscope has later been able 
to reveal to us? Has any one guessed the cross-striation of muscles, 
the cilia of vibratile epithelium, the prolongations of the nerve- 
cells, the make-up of the retina, or the organ of Corti, the chromo- 
somes, the centrosome? Distinctly not. Delage points out that 
the chemists had a much better chance to hit the truth in supposing 
atomic structure, for they had a much less complex condition to 
perceive, and they had approached in their positive knowledge very 
much nearer the hypothetical element which they adopted. 

Le Dantec criticises the micromeric theories of protoplasmic 
structure by saying that all these theories seek to make mysteries 

Le Dantec’s Clearer, complex things simpler, by reducing large 
criticisms, things to small ones. A man, for example (he says) 
is composed of 60 trillions of cells and is nevertheless produced by 
sexual elements of very small size; here is a phenomenon to ex- 
plain. The micromerist says that the difficulty of this explanation 
would be less (or at least not so sharply defined!) if one divided 
the problem into 60 trillions of parts; that is, if one replaced the 
reproduction of man by 60 trillions of partial reproduction. One 
has therefore imagined particles infinitely small which are to the 
cells what the sexual cells are to the man. And this comparison has 
been, consciously or not, claims Le Dantec, the point of departure 
of all the systems of particulate representation in the germ- 
plasm. 

We have simply substituted for a single heredity, continues the 
critic, 60 trillions of partial heredities, each exactly as mysterious 
as the first. Thus these 60 trillions of gemmules gathered in the 
egg and distributed in a precise manner are in reality only a dis- 
guising of the homunculus of the ovalists. Perhaps we have no 
reason to suppose that these gemmules design by their agglomeration 
this invisible homunculus, but at least it is certain that they 
are disposed in a manner which is in relation to the form of the 
man to be determined, since in fact each of them represents not 
alone a cell of the man, but a cell with the place it is to occupy. 

One sees thus how complex is this system which has for its aim 
the simplifying of the question of heredity: it is more logical to 
consider simply the egg as having the power to produce a man than 
to attribute a power as mysterious to 60 trillions of gemmules to 
which it is necessary to accord, in addition, a determinative capacity 


OTHER THEORIES: OF SPECIES-FORMING, 225 


which results in conducting each cell to exactly that place which 
it ought to occupy. 

In addition to the theories of an ultimate micromeric structure 
of protoplasm, certain other recent hypothetical explanations of 
Verworn’s bio- the special properties of protoplasm should be noted. 
gen hypothesis. One is the biogen hypothesis of Verworn, the physiol- 
ogist of Gottingen, one the chemism theory of Le Dantec, one 
the physical machine theory of Delage, and another is the general 
vital principle hypothesis of the neo-Vitalists. Verworn’s hypoth- 
esis to account for the physiological activities of protoplasm, 7. e., 
the special life attributes, as assimilation, disassimilation, growth, 
irritability, etc., consists in the postulation of a complex chemical 
compound of unknown structure called biogen, but with the special 
capacities of an enzyme. This biogen is assumed to be constantly 
labile, 7. e., breaking down and rebuilding itself and by this per- 
formance acting as a go-between (enzyme or perhaps katalysator) 
between the atmospheric oxygen brought to the cell by the blood 
and the oxidisable (food) products (also brought by the blood). 
Not only can the biogen rebuild itself, but by polymerisation it can 
grow, that is, increase the size of its molecules by adding side- 
chains of atoms. This, according to Verworn, constitutes cell 
growth. This growth is not indefinite, as the atoms tend to break 
away again and thus there is a limit to the size of the biogen mole- 
cules. The author only presents his conception of biogen as a good 
working hypothesis. 

Delage has also offered a tentative physico-chemical explanation 
of certain of the properties of protoplasm, as its movements, its 
Delage's ma- Nutrition, and even its reducing division, on the basis 
chine theory, of osmotic effects due to the constant interchange of 
substance from the outer layers of the cell protoplasm to the inner 
through fine membranes or special protoplasmic layers which he 
assumes to enclose each cell part, 1. e., nucleus, chromosomes, etc. 
Nutrition, for example, is effected according to Delage, by constant 
selective osmotic exchanges between the liquid and semi-liquid 
parts of the cell, the blood-plasm of course constantly bringing 
food and carrying off excreta to and from the periphery of each 
cell. Cell division is the result of mutual pulls and pushes, its 
essential feature always being the actual sundering of parts; but 
how this mechanical process is guided or controlled as it is, or even 
initiated, is left unexplained. ; 

Le Dantec holds that life is a chemical phenomenon. “La vie est 
Le Dantec’sthe- un phénoméne chimique, c’est-a-dire que les seuls 
ory of chemism. caractéres essentiels par lesquels tune action vitale 
différe d’une manifestation de l’activité de la matiére brute sont rela- 


226 DARWINISM TO-DAY. 


tifs a des destructions et des constructions d’édifices moléculaires. 
Cette vérité, toute la biologie nous la prouvera de mille maniéres; il 
vaut donc mieux l’énoncer en commengant, de manieére a ce qu'elle 
prenne la premiére place dans lJ’esprit de ceux qui se livreront 2 
Vétude des étres vivants. 

“Mais une réaction chimique n’est pas quelque chose disolé et 
ne se produit que dans certaines conditions dont la réalisation peut 
étre liée a des particularités d’ordre physique (chaleur, électricité, 
lumiére, etc.) ; de plus, elle s’accompagne toujours de phénoménes 
accessoires qui sortent également du domaine de la chimie (chaleur, 
mouvement, etc.). Ceci est vrai surtout pour les réactions des 
matiéres vivantes, a cause de l’état trés spécial de ce qui représente 
la solution de ces matiéres dans l’eau. La vie est aquatique, mais 
les matiéres vivantes ne se dissolvent pas comme du sel marin” 
(‘“Traité de Biologie,” pp. 43-44, 1903). 

He goes on to discuss, with keen analysis and ingenious but uncon- 
vincing synthesis, the various primary conditions and activities of 
life, explaining each vital phenomenon separately on a basis of 
chemism. He even proposes a chemical notion of species. Such 
a chemical species can of course take no primary account of form, 
but as conditions of chemical identity will usually involve identity 
of form, the various individuals composing a chemical species will 
possess a similar or identical form. An author, undertaking what 
Le Dantec undertakes, must necessarily be a bold thinker and a 
bold writer. The present author is both. And he is nowhere unin- 
teresting or unsuggestive, but also is he nowhere wholly con- 
vincing. 

The position of the neo-Vitalists is perhaps best to be taken 
from that of Driesch, an extremely able present-day biologist, whose 
first belief was in a radical mechanical explanation of 
all life phenomena, and whose brilliant experimental 
work has furnished many of the examples referred to in all text-books 
of the modern study of the mechanics of development. But Driesch’s 
present position is an uncompromising belief in the impossibility 
of explaining life-forms and life-functions on the basis of ever so 
complex a combination of purely physico-chemical and mechanical 
conditions and factors. Put positively, neo-Vitalism demands the 
assumption of an extra-physico-chemical factor (called “psychoid,” 
according to Driesch’s nomenclature), which is an _ attribute 
of, or essential kind of potentiality pertaining to, organised 
living substance, and not found in nor influencing inorganic 
bodies. 

Bitschli has well pointed out that neo-Vitalism is really only 
a return to the old “vital principle” belief, and that we are now, 


Neo-Vitalism, 


OTHER VW ILHEORIES (On SPECIES-FORMING, 227 


and have been ever since our practical giving up of the vital prin- 
ciple notion, making steady progress in the explanation of life- 
forms and life-functions on strictly mechanical and physico-chemical 
grounds. While we have by no means explained all life attributes 
in this way, Biutschli holds that our progress has been such as to 
make no demand for the introduction as yet of a new vital principle 
under a pseudo-scientific guise. 

Other neo-Vitalists, of whom G. Wolff is a type, lay chief stress 
on the inexplicableness of the Zweckmdssigkeit in organisms by 
any of the known biological facts and factors, and see in the deter- 
mination or very existence of this Zweckmdssigkeit the chief revela- 
tion of a vital factor, wholly distinct from anything found in the 
inorganic world. Wolff's argument is clever and suggestive, and 
brings home to one strongly the indissoluble relationship between 
living matter and its adaptivity. In its fundamental character life 
is adaptivity: the indispensable relation between living matter and 
the rest of nature is the pliability, the adaptiveness of the living 
matter. “Die zweckmdssige Anpassung ist das, was den Organis- 
mus sum Organismus macht, was sich uns als das eigentlichste 
Wesen des Lebendigen darstellt. Wir kinnen uns keinen Organts- 
mus denken ohne dieses Charakteristikum. ... Und wir erkennen 
dass jede Erklarung, welche das Leben voraussetzt, jede postvi- 
tale Erklarung der organischen Zweckmassigkeit, in jedem 
Falle voraussetzt was sie erklaren will; wir erkennen dass die 
Erklarung der Zweckmassigkeit mit der Erklarung des Lebens 
eusammenfallen muss.” 

But perhaps there is a difference between the plastic response of 
protoplasm to the varying conditions of oxygen, food, temperature, 
etc., about it, so that within certain limits of external versatility it 
still lives, and that extraordinary specialisation of fitness which we 
see exhibited by a parasitic Sacculina with relation to its crab 
host. And believers in natural selection hold that it is exactly one 
of the chief glories of selection that it does explain this highly 
specialised fitness. More than that, closer examination of the 
phenomena of organic Nature reveals many examples of an unfit- 
ness, which certainly ought not to exist if there is a special vital 
principle responsible for fitness throughout the organic kingdom. 
There is a moth common with us here in California, by name 
Phryganidia californica, whose larve live on the leaves of the oak- 
trees. Two generations appear each year. The eggs for the first 
brood of caterpillars are laid in spring by the moths on the leaves 
of the live-oaks and also of the white-oaks. The larve soon hatch, 
feed through thé summer on the leaves, and in September pupate, 
the moths appearing in October. These moths now proceed to lay 


228 DARWINISM TO-DAY. 


the eggs for the second generation, which eggs are also deposited 
on the leaves of both live- and white-oaks. But while the live-oak 
is an evergreen tree, the white-oak is deciduous, and sheds its 
leaves soon after these October eggs are laid on them, which means 
that one-half of this second generation is doomed to die of starva- 
tion immediately after hatching. This is repeated regularly each 
year, and is certainly a distinctly unfit habit in this moth’s life 
economy. Plate refers to a similar instance of Unzweckmdssigkeit 
as follows: ‘‘As I once was landing on Santa Maria Island in the 
Gulf of Aranco, the whole shore swarmed with thousands of giant 
cuttlefishes (Ommatastrephes gigas) which partly lay dead on the 
beach and partly were swimming around in the shallow water. 
These latter instead of trying to get back into deeper water, con- 
stantly swam towards the land until a breaker threw them up high 
and dry. Reflexes and instincts often make mistakes, that is, they 
result in actions which result in actual harm, and nothing is more 
mistaken than the declaration that an organism reacts under normal 
circumstances always in a way to serve the preservation of its life. 
That organisms under new circumstances or in abnormal condi- 
tion very often react unfitly, requires no elaboration; every light- 
house against which thousands of birds and insects are killed, the 
toxicological phenomena, the incomplete regeneration, every club- 
foot, and every Wasserkopf prove this. The countless harmful re- 


actions and incompletenesses in structure make it impossible to ~— 


speak, in the vitalistic sense, of an inherent Zweckmissigkeit“of 
organisms, of a tendency always to change in the direction of use- 
fulness. An organism is exactly as definitely ruled by chemico- 
physical laws as every dead body. Let an organism happen in any 
set of conditions: it has no longer the choice among a useful, a 
harmful, or an indifferent reaction, but the causal chain determines 
for a definite direction and this is, as a thousandfold observations 
show, not a life-preserving one, in other words is not zweckmdassig. 
If now in spite of this organisms have become, in the course of 
earth-history, even more complex and more capable and have 
acquired the most wonderful adaptation, there must obtain some 
regulatory principle in Nature, which we, with Darwin, recognise 
as actually existing in the struggle for existence and the con- 
sequent selection of fit variations. If organisms actually had the 
capacity to direct their vital activities always toward the side of 
utility, then the workings of the natural forces would be over- 
come and Mysticism again be introduced in. natural philosophy. 
Both actual observation and the theoretical basis of natural science 
give no basis for any hypothesis of the existence in organisms of 
an immanent capacity for adaptive reactions.” 


OTHER THEORIES OF SPECIES-FORMING. 229 


®* Weismann, A., “On Germinal Selection as a Source of Definite 
Variation,” trans. McCormack, p. 3, 1896. 

*T quote from Morgan, “Evolution and Adaptation,” pp. 165-166, 
1903, the following special protest against the means of escape from 


Morgan's criti- 2 tight place which Weismann has taken advantage of 


cism of Weis- in his dilemma: ‘Thus Weismann has piled up one 
mann’s method hypothesis on another as though he could save the 
of argument, integrity of the theory of natural selection by adding 


new speculative matter to it. The most unfortunate feature is that 
the new speculation is skilfully removed from the field of verifica- 
tion, and invisible germs whose sole functions are those which 
Weismann’s imagination bestows on them, are brought forward 
as though they could supply the deficiencies of Darwin’s theory. 
This is, indeed, the old method of the philosophisers of nature. An 
imaginary system has been invented which attempts to explain all 
difficulties, and if it fails, then new inventions are to be thought 
of. Thus we see where the theory of the selection of fluctuating 
germs has led one of the most widely known disciples of the Dar- 
Winian theory. 

“The worst feature of the situation is not so much that Weismann 
has advanced new hypotheses unsupported by experimental evi- 
dence, but that the speculation is of such a kind that it is, from its 
very nature, unverifiable, and therefore useless. Weismann is mis- 
taken when he assumes that many zoologists object to his methods 
because they are largely speculative. The real reason is that the 
speculation is so often of a kind that cannot be tested by observa- 
tion or by experiment.” 

“Roux, W., “Der Kampf der Theile im Organismus,” 188r. 

* Baldwin, J. Mark, “A New Factor in Evolution,” Amer. Nat., 
Vol. XXX, pp. 441 ff., 1896; see also the same author’s ‘“Develop- 

References to ment and Evolution,” chap. viii, 1902; in the appen- 
discussions of dices of this book is given a detailed history of the 
orthoplasy, independent formulation of the theory of “Organic 
Selection or Orthoplasy,” by Baldwin, Osborn, and Morgan. 

* Osborn, H. F., “A Mode of Evolution requiring neither Natural 
Selection nor the Inheritance of Acquired Characters,” Trans. New 
York Acad. Sct., pp. 141-148, 18906; also Science, April 3, 1896; also 
Amer. Nat., Nov., 1897. From this last reference I quote the 
following concise statement of the theory: ‘‘This hypothesis as it 
appears to myself is, briefly, that ontogenic adaptation is of a very 
profound character; it enables animals and plants to survive very 
critical changes in their environment. Thus all the individuals of 
a race are similarly modified over such long periods of time that, 
very gradually, congenital variations which happen to coincide with 


230 DARWINISM TO-DAY. 


the ontogenic adaptive modifications are collected and become 
phylogenic. Thus there would result an apparent but not real 
transmission of acquired characters.” 

*°? Morgan, C. L., ‘“Habit and Instinct,” pp. 312 ff., 1896; see also 
Science, pp. 793 ff., Nov., 1896. In Appendix C of Baldwin’s ‘“De- 
velopment and Evolution,’ p. 347, 1902, is the following clear 
statement (in letter to Baldwin) of Morgan’s conception of organic 
selection: i 

“tr. On the Lamarckian hypothesis, racial progress is due to the 
inheritance of individually acquired modifications of bodily struct- 
ure, leading to the accommodation of the organism or race to the 
conditions of its existence. 

“2. This proposition is divisible into three: (a) Individual prog- 
ress is due to fresh modifications of bodily structure in accommo- 
dation to the conditions of life. (b) Racial progress is due to the 
inheritance of such newly acquired modifications. (c) The evolu- 
tion of species is the result of the cumulative series— 

‘“a>b+a'>b’+a">b"+a'">b'", etc., etc., where a, a’, a”, a’ are 
the acquisitions, and b, b’, b’’, b’’” the cumulative inherited results. 

“3, Anti-Lamarckians do not accept (b) and (c). But they 
accept (a) in terms of survival. No one denies that individual 
survival is partially due to fresh modifications of bodily structure 
in accommodation to the conditions of life. 

“4. It logically follows from 3 that individual accommodation is a 
factor in survival which cooperates with adaptation through ger- 
minal variation. 

“Weismann, following the lead of Roux, interpreted individual 
modification in terms of intra-selection. He clearly saw the impli- 
cation given in 4 above. Speaking of ‘the well-known instance of 
the gradual increase in the development of deers’ antlers,’ he says 
(Romanes Lecture, 1804, p. 18): ‘It is by no means necessary 
that all the parts concerned should simultaneously adapt them- 
selves by variation of the germ to the increase in size of the antlers; 
for in each separate individual the necessary adaptation [accommo- 
dation] will be temporarily accomplished by intra-selection—by the 
struggle of parts—under the trophic influence of functional 
stimulus.’ 

“6. So far there is no direct relation between specific modifications 
and specific variations. Individual accommodation, as a factor 
in survival, affords time (Weismann, op. cit., p. 19) for the occur- 
rence of any variations of an adaptive nature. 

“7 My own modest contribution to the further elucidation of 
the subject is the suggestion (1) that where adaptive variation v 
is similar in direction to individual modification m, the organism 


OTHER THEORIES OF SPECIES-FORMING. 23U 


has an added chance of survival from the coincidence m+v; (2) 
that where the variation is antagonistic in direction to the modifica- 
tion, there is a diminished chance of survival from the opposition 
m—v; and hence (3) that coincident variations will be fostered 
while opposing variations will be eliminated. 

“8. If this be so, many of the facts adduced by Lamarckians 
may be interpreted in terms of the survival and gradual establish- 
ment of coincident variations by natural selection under the 
favourable environing conditions of somatic modifications. 

“9. It is clear that there is nothing in this suggestion of a direct 
relation between specific accommodation and coincident variation 
which can be antagonistic to the indirect relation indicated above 
in 6. 

“to. Correlated and coexistent variations would have the same 
relations to coincident variations as obtain in other cases of natural 
selection.” 


CHAP TEREX. 


OTHER THEORIES OF SPECIES-FORMING AND 
DESCEND (CONTINUED \ir AX LISTAT Yes biases 
ORIES (CONTINUED). 


Isolation Theories —The varying importance attributed 
by different biologists to the theories explaining means 
and results of isolation is notable. While by 

Importance of : ; : : : 
the isclation  SOMe the species-forming influence of isolation 
fea species- jg held to be as effective as selection itself,— 
some deem it more effective,—others attach but 
little importance to it, indeed see no effects of consequence. 
These latter men are likely to be morphologists, cytologists, 
and laboratory men generally; the former are systematists, 
students of distribution, and so-called field naturalists. Thus 
Delage, who gives much attention in his general discussion 
of the theories of heredity, variation, and species-forming 
to many purely speculative theories of the ultimate structure 
and behaviour of protoplasm, and of the mechanism of 
heredity, dismisses the whole subject of geographic and 
topographic isolation with a couple of superficial para- 
graphs, in which he presents a singularly fallacious state- 
ment of what the effects of isolation should be. On the 
other hand the veteran German world-voyager and exploring 
naturalist, Moritz Wagner, established long ago, on the basis 
of his observations and deductions, a “law” of species-form- 
ing by migration and consequent isolation, which in his *mind 
makes the natural selection theory superfluous. And Henry 
Seebohm in a discussion of Romanes’s* formulation of the 
principle of physiological selection, says: “So far as is 

232 


OTHER THEORIES OF SPECIES-FORMING, 233. 


known, no species (of birds) has ever been differentiated 
without the aid of geographical isolation, though evolution 
may have gone on to an unknown extent; and, so far as we 
can judge, geographical isolation must always, sooner or 
later, be followed by differentiation.” And Romanes, him- 
self, conspicuous as the only pupil and disciple of Darwin 
personally advised and aided by the master himself, and one 
of the most brilliant upholders and expositors of Darwin- 
ism, says: “Indeed I believe with Mr. Gulick, that in the 
principle of isolation we have a principle so fundamental. 
and so universal, that even the great principle of natural. 
selection lies less deep and pervades a region of smaller 
extent. Equalled only in its importance by the two basal 
principles of heredity and variation, this principle of isola- 
tion constitutes the third pillar of a tripod on which is reared 
the whole superstructure of organic evolution.” Thus the 
most ardent believers in the effects of isolation find it, inde- 
pendent of selection and alone, sufficient to explain species-. 
forming, while the most ardent neglecters of isolation theo- 
ries find them too slight to be of any consequence at all. We 
shall take middle ground and find in isolation a factor of 
ereat effectiveness and one wide-spread in its influence in 
helping to produce the present-day status of the animal 
kingdom, but yet a factor which shall most fairly be looked 
on as an auxiliary or helping-theory of natural selection. In 
fact, tomy mind, the proof of the species-establishing effects. 
of isolation, and of the actual existence of isolation (proof 
of means or modes of isolation), is something much needed 
by the general natural selection theory for its own sup- 
port. Selection needs help from isolation. To my mind, 
also, these means of isolation actually exist, and the result- 
ing isolation is actually a very potent factor in species-form- 
ing. The proofs seem to me obvious. 

The name isolation fairly well defines the condition that 
we are to discuss; (the term segregation has also been used. 


234 DARWINISM TO-DAY. 


by some authors to name the same condition). l1, in a 
species, a number of individuals show a certain congenital 
variation, this variation will probably be lost by 
cross-breeding with individuals not having it, 
unless the individuals having it are in the ma- 
jority or unless they become in some way isolated from the 
others and segregated so that they will breed among them- 
selves. By such isolation and such in-and-in breeding the 
newly appearing congenital variations might soon become 
established, and if advantageous be so considerably developed 
as soon to distinguish as a variety or incipient species the 
members of the isolated colony. With time a distinct new 
species might result. Are there means to produce such isola- 
tion of groups of individuals belonging to a common species? 
The answer to this is certainly an affirmative one. There 
seem to be, indeed, several means of producing isolation, 
SAN aa and the isolation may be variously named ac- 
of effecting iso- cordingly. Undoubtedly the most important of 
Eck these kinds of isolation, at least in the light of 
our present knowledge, is that known as geographical or 
topographical isolation. Isolation produced in other ways 
may be called biologic or physiologic or sexual isolation. 
In the case of geographic or topographic isolation the iso- 
lated group or groups of individuals are actually in another 
region or locality from the rest of the species, this being 
the result of migration, voluntary or involuntary. In bio- 
logic isolation the individuals of the species all inhabit the 
same territory but become separated into groups by struc- 
tural or physiological characters which prevent 

pike sas col miscellaneous inter-breeding. The real founder 
theory of species- and most insistent uphoider of the theory of 
Hie: ae species-forming by isolation (geographic and 
topographic isolation), was Moritz Wagner’ 
(1813-1887), a traveller and naturalist, whose wanderings 
and observations brought to him the conviction that while 


What is meant 
by isolation. 


OTHER THEORIES OF’ SPECIES-FORMING., 235 


natural selection might modify species and even produce 
continuous evolution it could never differentiate species, 
that is, produce new species. It could never, in Wagner’s 
belief, produce the actual condition which we know to exist 
in the present-day and past (now extinct) animal kingdom, 
this condition being the existence of hosts of distinct, though 
related, animal species or kinds. Wagner’s travels included 
journeys to North, Central, and South America, West Asia, 
and North Africa. His first clear enunciation of his theory, 
in which pronouncement he took definite stand against 
the claimed capacity of Darwinian selection to produce new 
species, was in 1868, in a paper read in’ Munich,, entitled 
“Die Darwinische Theorie und das Migrationsgesetz der 
Organismen.” From the time of the appearance of this 
first paper until within a year or two of his death, Wagner 
steadily wrote and fought for his theory, but without gain- 
ing for it any such wide or authoritative acceptance as he 
hoped. Ina letter dated August 30, 1884, Wagner pathet- 
ically writes, “Ich sterbe mit der Uberzeugung, dass man 
dies wenigstens nach meinem Tode anerkennen wird.” 
Wagner’s theory included not only the characteristics 
already pointed out as the basis of all theories of the influ- 
ence of isolation in species-forming, but the assumption that 
all species of animals have a strong tendency, or are con- 
stantly attempting, to “spread out’; that is, have a driving 
instinct of migration and dispersal. The basis of this 
tendency is undoubtedly the overcrowding in the immature 
stages and in times of short food-supply or untoward exter- 
nal conditions of temperature, humidity, etc. This tendency 
to movement is Wagner’s “Migrationsgesetz,” and the out- 
come of it is to bring about conditions of topographic and 
geographic isolation among all kinds of animals. While in 
his first papers Wagner looked on his theory as a sort of 
supporting or auxiliary theory to that of natural selection, 
he soon began to see in it, calling it now by the name of 


236 DARWINISM TO-DAY. 


“Separationstheorie,’ an independent and alternative expla- 
nation of species-forming. In 1870, he wrote: “Um den 
Unterschied beider Theorien moglichst kurz auszudriicken: 
nach der Darwin’schen Selectionstheorie zuchtet die Natur 
in Folge des Kampfes ums Dasein rastlos neue typische 
Formen der Organismen durch Auslese nutzlicher Varieta- 
ten, gleichviel ob inner- oder ausserhalb des Verbreitungs- 
gebietes der Stammart, und kann diesen Prozess der Bil- 
dung einer neuen Art nur innerhalb eines sehr langen 
Zeitraumes vollziehen. 

“Nach der Separationstheorie ziichtet die Natur nur 
periodisch neue Formen stets ausserhalb des Wohngebietes 
der Stammart durch geographische Isolierung und Kolo- 
nienbildung, ohne welche bei allen hoheren Tieren getrenn- 
ten Geschlechts keine konstante Varietat oder neue Art 
entstehen kann. Der Gestaltungsprozess einer neuen Form 
kann nicht von langer Dauer sein.” 

Or in still more condensed form: . . . “Nach der Selek- 
tionstheorie ist der Kampf ums Dasein, nach der Separa- 
tionstheorie die ratumliche Absonderung, die nachste zwing- 
ende Ursache der Artbildung.” 

Wagner’s latest, most definitive, cleanest cut, single 
formulation of the Separationstheorte is that contained in 
two paragraphs in his essay entitled, “Leopold von Buch 
und Charles Darwin” (Kosmos, 1883). These paragraphs 
are the following: : 

“Tt. Jede dauernde ratimliche Absonderung einzelner oder 
weniger Emigranten von einer Stammart, welche noch im 
Stadium der Variationsfahigkeit steht, erzwingt auf Grund 
der Variabilitat und der Vererbung eine konstante Diffe- 
renzierung, indem sie unter Mitwirkung veranderter Le- 
bensbedingungen, die jeden Standortswechsel begleiten, 
auch die minimalsten individuellen Merkmale der ersten 
Kolonisten bei blutsverwandter Fortpflanzung fortbildet 
und befestigt. 


OTHER THEORIES OF SPECIES-FORMING, 237 


“2. Keine konstante Varietat oder Art entsteht ohne 
Ausscheidung einzelner oder weniger Individuen von der 
Stammart und ohne Ansiedelung an einem neuen Standort, 
weil Massenkreuzung und Gleichheit der Lebensbedin- 
gungen in einem zusammenhangenden Wohngebiet immer 
absorbierend und nivellierend wirken mtssen und indivi- 
duelle Variationen stets wieder in die Stammform zurtick- 
drangen.” . 

Wagner’s ° long series of interesting papers and addresses 
are crammed with facts of plant and animal geography, 
taxonomy and paleontology, and with keen interpretation 
of these facts, and clear and incisive formulations of his few 
generalisations. 

One of the most ardent present-day upholders of the 
species-forming potency of geographical isolation is David 
Starr Jordan, the foremost American student of the classi- 
fication and distribution of fishes. From a recent paper ' 
I abstract the following brief statements of his beliefs con- 
cerning the character and results of the influence of geo- 
graphical isolation. 

“It is now,” writes Jordan, “nearly forty years since 
Moritz Wagner (1868) first made it clear that geographical 

Preaie isolation (raumliche Sonderung) was a factor 
geographic or condition in the formation of every species, 
ea aucr race, or tribe of animal or plant we know on 
the face of the earth. This conclusion is accepted as almost 
self-evident by every competent student of species or of 
the geographical distribution of species. But to those who 
approach the subject of evolution from some other side the 
principles set forth by Wagner seem less clear. They have 
never been confuted, scarcely even attacked, so far as the 
present writer remembers, but in the literature of evolution 
of the present day they have been almost universally ignored. 
Nowadays much of our discussion turns on the question of 
whether or not minute favourable variations would enable 


| 


\ 


238 DARWINISM TO-DAY. 


their possessors little by little to gain on the parent stock, 
so that a new species would be established side by side with 
the old, or on whether a wide fluctuation or mutation would 
give rise to a new species which would hold its own-in com- 
petition with its parent. In theory, either of these condi- 
tions might exist. In fact, both of them are virtually un- 
known. In nature a closely related distinct species is not 
often quite side by side with the old. It is simply next to it, 
geographically or geologically speaking, and the degree of 
distinction almost always bears a relation to the importance 
or the permanence of the barrier separating the supposed 
new stock from the parent stock. 

“A flood of light may be thrown on the theoretical prob- 
lem of the origin of species by the study of the probable 
actual origin of species with which we may be familiar, or 
of which the actual history or the actual ramifications may 
in some degree be traced.” 

Dr. Jordan then proceeds to relate and analyse our pres- 
ent actual knowledge of the make-up of certain local faune, 
of the migrations and distribution of certain well-known 
animal species (especially in the phyla of birds and fishes, 
in which groups our knowledge of the present status in 
North America of species and varieties and their distribu- 
tion is nearly exhaustive), and of the climatic, topographic, 
and general geographic barriers * which determine this dis- 
tribution, in a way most convincing to unprejudiced minds. 
He brings to the support of his own statements of fact and 
opinion the testimony (contained in personal letters an- 
swering direct queries from himself) of many well-known 
American students of systematic and faunistic zoology. 
Jordan sums up the results of his display of North Ameri- 
can faunal conditions in various paragraphs, from among 
which the following are quoted: | 

“In regions broken by few barriers, migration and inter- 
breeding being allowed, we find widely distributed species, 


OTHER THEORIES OF. SPECIES-FORMING. 239 


homogeneous in their character, the members showing indi- 
vidual fluctuation and climatic effects, but remaining uni- 
form in most regards, all representatives slowly changing 
together in the process of adaptation by natural selection. 
In regions broken by barriers which isolate groups of indi- 
viduals we find a great number of related species, though in 
most cases the same region contains a smaller number of 
genera or families. In other words, the new species will be 
formed conditioned on isolation, though these same barriers 
may shut out altogether forms of life which would invade 
the open district. 

“Given any species in any region, the nearest related 
species is not likely to be found in the same region nor in 
a remote region, but in a neighbouring district separated 
from the first by a barrier of some sort. 

“Doubtless wide fluctuations or mutations in every species 
are more common than we suppose. With free access to the 
mass of the species, these are lost through interbreeding. 
Tsolate them as in a garden or an enclosure or on an island, 
and these may be continued and intensified to form new 
species or races. Any horticulturist will illustrate this. 

“In these and in all similar cases we may confidently 
affirm: The adaptive characters a species may present are 
due to natural selection or are developed in connection with 
the demands of competition. The characters, non-adaptive, 
which chiefly distinguish species do not result from natural 
selection, but from some form of geographical isolation and 
the segregation of individuals resulting from it. 

“In the animal kingdom, generally, we may say: When- 
ever a barrier is to some extent traversable, the forms 
separated by it are liable to cross ffom one side to the other, 
thus producing intergradations, or forms more or less 
intermediate between the one and the other. For every 
subspecies, where the nature of the variation has been care- 
fully studied, there is always a geographical basis. This 


ad 


240 DARWINISM TO-DAY. 


basis is defined by the presence of some sort of a physical 
barrier. It is extremely rare to find two subspecies inhabit- 
ing or breeding in exactly the same region. When such 
appears to be the case, there is really some difference in 
habit or in habitat; the one form lives on the hills, the other 
in the valleys; the one feeds on one plant, the other on 
another; the one lives in deep water, the other along the 
shore. There can be no possible doubt that subspecies are 
nascent species, and that the accident of intergradation in 
the one case and not in the other implies no real difference 
in origins. 

“To the general rule that closely allied species do not live 
together there exist partial exceptions. It may be well to 
glance at some of these, for no rule is established until its 
exceptions are brought into harmony with the phenomena 
which illustrate the rule.” (Here Dr. Jordan details the 
facts of distribution in three cases from among the fishes, 
which apparently form exceptions to his general rule). 

As an example of the effects of an unusual and interesting 
phase of isolation I may refer to the conditions noted con- 

aH ohee cerning the distribution and species distinction 
isolation inthe Of the Mallophaga, a group of small wingless 
Mallophaga. = insect parasites on birds and mammals. These 
parasites live for their whole lives among the feathers or 
hair of their hosts, and while able to run swiftiy are unable 
to fly and thus to migrate freely from bird to bird. 

“There are to be noted various results of the influence on 
the taxonomy of the Mallophaga of the peculiar conditions 
of their parasitic life. While the uniformity and persistence 
of the conditions under which the life of the parasites is 
passed tend to preserve with little change the species types, 
the peculiar isolation, often pretty complete, of groups of 
individuals of a parasite species on individual birds of the 
host species and the consequent close breeding, tend to 
foster and fix those inevitable slight variations always mani- 


OTHER THEORIES OF SPECIES-FORMING. 247 


fest in a comparison of offspring and parents, but under 
normal conditions held in check or lost (unless directly 
advantageous) by crossing among less closely related indi- 
viduals. For example, the individuals of a parasite species 
on a bird of long life and non-gregarious and monogamous 
habits, like an eagle, live very much the life of an isolated 
community. There must be many years of in-and-in breed- 
ing. Itis like island life. The result is certain: the members 
of this isolated group will soon differ from the specific 
type in noticeable particulars. On the other hand, the con- 
ditions of life on this ‘island’ are practically identical with 
the conditions on other similar ‘islands’-—other eagles—in- 
habited by other individuals of the same parasite species, so 
there is no influence working to produce a wide divergence 
of the members of these various isolated groups of indi- 
viduals of the same species. Now this isolation of groups of 
individuals is in some degree an incident of the life of all 
Mallophaga; in some instances it is considerable; in others, 
inconsiderable, but taken altogether a condition in the life 
of the whole order exerting an influence which has the 
readily recognisable result of creating a great number of 
small variations within species limits. 

“The results, manifest to any student of the group, of 
these two opposing influences are to render difficult the divi- 
sion of the order into distinct genera on account of the gen- 
eral similarity of structure, and to make difficult the defini- 
tion of species on account of the many slight variations 
among the individuals from different bird individuals.” ” 

The study of geographic distribution and its influences on 
species-forming has not been limited, of course, to living 

Geographic Organisms alone. In fact, the geologic study 
Tae sae of distribution and migration of both animals 
animals, and plants has given us some of our most 
important facts touching the problem of the influence of 
isolation on species-transformation. In an interesting paper 


242 DARWINISM TO-DAY. 


on the “geological study of the migration of marine inverte- 
brates,” Smith *® has pointed out the general principles and 
conditions upon which the interpretation of the geographic 
distribution of the marine invertebrates of the earlier geo- 
logic ages must be based. 
In closing this consideration of the status of geographic 
isolation as a factor in species-forming, I should not omit to 
Isolation not Call attention to the fact, which should be obvi- 
cede ous enough to any reader, that isolation in itself 
forming, cannot be the basic and all-sufficient cause for 
the production of specific differentiation, any more than any 
selective factor can ne prerequisite in both cases is the 
occurrence of variation. What are the variations, and how 
are they produced: these are the fundamental questions in 
species-forming. Isolation is a tremendously favouring con- 
dition but not a primary cause of species-forming. It tends 
to help along, to hurry up species disintegration, not to 
initiate it. It is a biological catalytic agent. 
| //In this present connection the pertinent question is, is the 
influence of geographical isolation in the cumulation of 
/ variation or intra-specific differentiation due to its com- 
pelling in-and-in breeding and hence the fostering and cumu- 
lation of fortuitous Darwinian variations occurring in the 
comparatively few individuals of the isolated group, or is 
there a spur to variation, or even actual production of it along 
determinate lines, in the new environmental conditions com- 
mon to all the isolated group but inevitably different from 
the conditions to which the parent type is exposed? Is there 
a gradual accumulation of differences between the split-off 
group and the parent group due to environmental influence 
plus in-and-in breeding? If we could reply yes to this 
question, we should have a sufficient explanation of 
how the isolated group splits rapidly away in many 


small, and in a few large, characteristics from the parent 
stock, 


OTHER THEORIES” OF SPECIES-FORMING, 243 


From the foregoing it is obvious that geographical isola- | 
tion is a proved, effective, and widely applied species-form- — 


ing factor. So much cannot be said for biologic 
and sexual isolation.” The actual existence of 
such isolation is not proved by any mass of evi- 
dence based on observation, although the theory is by no 
means pure speculation; nor are the results of such isola- 
tion clearly indicated, although a certain amount of observa- 
tion and experimental evidence can be adduced to show 
them. The different phases of isolation, not geographic, 


Biologic 
isolation, 


called by different names, as biologic, physiologic, sexual,( 


and morphologic isolation, all have reference to some sort | 


of segregation of individuals of the same species into groups 
inside of each of which mating takes place, and among 


Thane erin ado ¥ 


which little or no cross-breeding occurs, because of varying ° 


habits, or unusual sexual aversion or attraction, or physio- 
logical or morphological variation affecting mating. For 
example, to take first a sort of combination of geographic 
and biologic isolation, Plate** points out that there are 
twelve species of albatrosses in the southern hemisphere, of 
which nine or ten belong to the Australian zoo-geographical 
realm and intermingle throughout most of their range. At 
breeding time, however, these different species become 
segregated in restricted and separate localities so that mating 
is always accomplished among different individuals of the 
same species, although hybridisation could doubtless obtain 
successfully among these closely related albatross forms. 
Thus the species characters are kept pure; the species dis- 
tinct. 

An example of pure biological isolation and one within 
a single species (which is the sort of isolation we are more 

Anexampleof interested in) might be produced in the follow- 
ede eunt ing way. We know of numerous species of 
work, butterflies which appear in different seasons of 
the year in different colour-pattern. This is not a colour 


244 DARWINISM TO-DAY. 


change in individuals but results from an earlier or later 
hatching of eggs laid in the autumn or summer before. 
These eggs may, indeed, be all of one batch or lot, laid by a 
single female. Some of these eggs hatch in the spring; the 
butterflies that come from these spring larve are of one col- 
our-pattern ; some of the eggs, however, delay hatching until 
summer; from these larve come butterflies of another 
colour-pattern; some of the eggs even go over until fall 
before hatching; these latest butterfly individuals may be of 
a third colour-pattern. The colour-pattern here must have 
some fixed relation to the time or season of hatching of the 
eggs; it is not a result of isolation. But the condition well 
illustrates the actual existence of a biological isolation within 
a species: the spring butterflies must mate among them- 
selves, the summer individuals among themselves, and the 
fall butterflies among themselves. Within the one species 
are three biologically isolated groups of individuals re- 
strained from inter-breeding. Suppose. the individuals of 
a bird species show among themselves a tendency to vary 
in their breeding time ; some are ready to breed early, others 
delay mating. Roughly segregated into two groups, early 
breeders and late, the individuals of the two groups would 
obviously tend to breed each inside its own group. Hut- 
ton ** actually records the occurrence of two varieties of the 
shore-bird, Cstrelata neglecta, in the Kermadec Islands, 
which live together but breed at different times. A pelagic 
crustacean living near the shore increases rapidly in num- 
bers; some individuals find themselves able to live on the 
shore in pools between tide-lines. The pool dwellers breed 
together: the pelagic individuals breed together ; a biologic 
isolation—in truth an isolation partly topographic—might 
soon come to exist. Any variation in habits of life among 
individuals living in the same locality, which tends to deter- 
mine that breeding shall be roughly restricted within cer- 
tain groups produces biologic isolation; such variation might 


OTHER THEORIES: OF “SPECIES-FORMING, 245 


be a variance in sexuai maturity, a change in breeding time 
for that or any other reason, a tendency on the part of cer- 
tain individuals to live more or less concealed in holes, under 
stones, etc., changes in food-habits, as the gradual going 
over of some individuals of a plant-feeding insect species 
from the old food-plant to a new one, or the tendency within 
an omnivorous species for groups to restrict themselves to 
certain specific foods: all such variations might lead to pos- 
sible biological isolation. 

By sexual isolation authors usually refer to the influ- 
ence of some variation tending to make difficult or impossi- 

Shs ble wholly free and miscellaneous mating or 
isolation, breeding inside of a species. This variation 
may be of purely physiological character or may be a struc- 
tural one: that is, the hindrance to mating may be one of 
instinctive feeling, a “race-feeling’”’ depending on an antipa- 
thy to odour, to age, to appearance, etc., or may be a slight 
modification of the copulatory organs making such mating 
difficult, or even a modification of the egg or the spermato- 
zoids making fertilisation difficult. It is a well-known fact 
that numerous varieties of domesticated animal species 
rarely breed together, although quite able to, and provided 
with full opportunity. On the other hand, animals of differ- 
ent species which in Nature rarely or never breed together 
may, if kept long in confinement, as in zoological gardens, 
mate ** and produce young. In each case there seems to be 
question of a “race-feeling”’; in the first case a sexual 
aversion keeping apart individuals of the same species, in 
the second the breaking down of race-feeling that in Nature 
has sufficed to prevent hybridising. This might be termed 
physiological isolation, or, indeed, physiological selection, as 
it has been called, and given much credit for 
species-forming by Romanes**® and _ others. 
Romanes and Hutton believe that a progressive 
infertility results in this way (and also by the way referred 


Physiological 
selection, 


246 DARWINISM TO-DAY. 


to in the next paragraph) which can soon result in complete 
infertility, hence specific distinctness on the part of the 
mutually infertile groups. 

_ Mutual infertility due to morphological variations has 
been called “mechanical selection” by Karl Jordan,* and 
may rest on slight variations in germ-cells or 
copulatory structures. Such morphological 
variations of the reproductive organs have been 
believed to be shown for butterflies and spiders, while the 
delicate tropismic responses of the active spermatozoids to 
the attracting chemical substances in the egg-cells of echino- 
derms, ccelenterates, molluscs, and fishes have been thought 
to be conditions in. which a slight chemical or physical varia- 
tion might have a large influence in preventing or insuring 
fertilisation. Indeed, when one examines comparatively the 
curiously various complex accessory reproductive organs 
(claspers, gonapophyses, intromittent organs, etc.) of almost 
any group of insects, one’s first thought is that this variety 
must practically effectually exclude all possibility of hybri- 
dising. But the interesting detailed comparative studies 
by Snodgrass *" of the accessory genitalia in various families 
of Diptera make this confidence less certain. In the large 
family Tipulide, for example, he finds great complexity 
and remarkable variety (among the different closely allied 
species) in this complexity in the genitalia of the males, but 
almost no variation at all in the corresponding (complement- 
ary) parts of the females. “Throughout the entire family 
the females present one type of structure, of which there is 
but little modification, and certainly none to correspond with 
the great variety of specific differences found in the genitalia 
of the males.” Now while the great variety of the copula- 
tory parts would be extremely significant if shared by both 
sexes so that only one kind of key could fit one kind of lock, 
we have the inexplicable condition actually existing of the 
keys being extremely various and complex, but the locks all 


Mechanical 
\ selection. 


OTHER THEORIES OF SPECIES-FORMING. 247 


being so similar and simple that any bent nail is able to pick 
them. 

Seebohm ** criticises Romanes’s theory of physiological 
selection, which should better be called physiological 


Seebohm’s isolation, as demanding an almost impossible 
peo say OF coincidence of conditions to make it work. 
physiologic se- / : ‘ 
lection. Formulated as nearly as it can be in a single 


sentence, Romanes has defined physiological selection as 
follows: ‘““Wherever, among all the possible variations of 
the highly variable reproductive system there arises toward 
any parent form any degree of sterility which does not 
extend to the varietal form, there a new species must neces- 
sarily take its origin.” Seebohm points out that this is 
exactly a condition that can rarely, if ever, occur, for to 
bring it about we must presuppose :— 7 

“tst. The special variation of the reproductive organs 
must occur in two individuals, otherwise the possible an- 
cestor of the new species would leave no descendants. 

“2d. It must occur at the same time in both. 

“3d. It must occur at the same place. 

“ath. The two individuals must be of opposite sexes. 

“sth. They must each of them possess some other varia- 
tion, or their progeny would not differ from that of the rest 
of the species. 

“6th. The variation must be the same in both or appear 
simultaneously in the majority of their children, otherwise 
it would be swamped by interbreeding within the physio- 
logically isolated family.” 

Romanes’s theory has also been strongly criticised by 
Wallace * and by Karl Jordan.*” Wallace contends that 

okie critloiems 1° form of infertility or sterility between the 
of Romanes’'s individuals of a species can be increased by 
ate natural selection unless correlated with some 
useful variation, while all unfertility not so correlated has a 
constant tendency to effect its own elimination. But the 


248 DARWINISM TO-DAY. 


opposite property, fertility, is of vital importance to every 
species, and gives the offspring of the individuals which 
possess it, in consequence of their superior numbers, a 
greater chance of survival in the battle of life. It is, there- 
fore, indirectly under the control of natural selection, which 
acts both for the self-preservation of fertile and the self- 
destruction of unfertile stocks—except always, as correlated 
above, when they become useful and therefore subject to be 
increased by natural selection.” Jordan maintains that the 
outcome of physiological selection can be at best only 
dimorphism, not specific distinctness. 

Vernon ~* has formulated a theory which he calls that of 
“reproductive divergence,’ in the following words: “Sup- 


Vernon's posing that among the members of any species 
theory of repro- those individuals more alike in respect to any 
ductive diver- i ae 
gence, different characteristic, such as colour, form, or 


size, are slightly more fertile inter se than less similar indi- 
viduals, it necessarily follows that in the course of succeed- 
ing generations the members of this species will diverge 
more and more in respect to the characteristic in question, 
whereby ultimately the original species may be split up into 
two or more fresh species.’’ As a concrete example, Vernon 
supposes that in the Lepidopterous Jthania urolina, a certain 
insect found in the Amazon Valley, small individuals were 
slightly more fertile with other small individuals than with 
large individuals, while these were also more fertile inter se; 
“then it would follow that fewer individuals of intermediate 
size would be produced, and in course of time the species 
would be split up into a small and large variety. These 
varieties would continue to diverge as long as the process 
of ‘reproductive divergence’ was acting, till at length they 
might become differentiated in the two mutually sterile 
species. Supposing on the other hand this variation in 
fertility were correlated with slight differences of colour, 
then in course of time varieties differing in respect of colour 


OTHER THEORIES) OF SPECIES-FORMING, 249 


would be produced; or if it were correlated with both size 
and colour, varieties differing in respect of both characters 
might be produced. As a matter of fact, this insect does 
actually occur as four distinct varieties differing in colour, 
form, and size, though whether in consequence of the oper- 
ation of reproductive divergence it is of course impossible 
to say.” But this theory has been strongly criticised by 
Karl Jordan,** who believes himself able to show that re- 
productive divergence would not work in the way conceived 
by Vernon, but actually in such a way as to establish an 
intermediate form. 

Karl Pearson ** has formulated a theory called ‘“reproduc- 
tive selection” which he believes to be distinct from both the 

Seon Romanes and the Vernon theories, and to which 
theory of repro- he attributes an importance in evolution “equi- 
ductive selection.  otent to natural selection, if indeed it be not 
prepotent.” The theory is based on correlations which seem 
to exist between the variation in some particular organ and 
fertility. From studies of variation of height in 4,000 Anglo- 
Saxon families and 1,182 Danish families, Pearson finds © 
that there exists a distinct correlation between fertility and 
height in the mothers of daughters in these families. The 
effect of this correlation is to render women less variable 
and to raise their mean height. The quantities are small, 
but are sufficient, if unchecked by natural selection, to raise 
the mean height of women in forty generations by 3 1-4 
inches. “A factor which would alter stature by about three 
inches in 1,000 years is clearly capable of producing very 
considerable results in the long periods during which evolu- 
tion may be supposed to have been at work.” 

Of large importance in any consideration of the relations 

Gulick’sim- Of isolation to species-forming are the observa- 
portant dbserv@- tions and conclusions of Gulick. Derived origi- 
sions, nally from an exhaustive study of the variation 
and life-conditions of certain land shells (Achatinellidze) 


250 DARWINISM TO-DAY. 


in the Hawaiian Islands, he formulated, in 1872, an im- 
portant principle concerning the species-differentiating ef- 
fects of indiscriminate isolation. As Romanes ** well points 
out, isolation may not only admit of degrees, that is, 
may be either total or partial, and, if partial, may occur 
in numberless grades of efficiency, but it may be either dis- 
criminate or indiscriminate. If it be discriminate, the isola- 
tion has reference to the resemblance of the separated indi- 
viduals to one another ; if it be indiscriminate, it has no such 
reference. For example, if a shepherd divides a flock of 
sheep without regard to their characters, he is isolating one 
section from the other indiscriminately ; but if he places all 
the white sheep in one field and all the black sheep in another 
field, he is isolating one section from the other discriminately. 
Or, if geological subsidence divides a species into two parts, 
the isolation will be indiscriminate; but if the separation be 
due to one of the sections developing, for example, a change 
of instinct determining migration to another area, or occu- 
pation of a different habitat on the same area, then the isola- 
_ tion will be discriminate, so far as the resemblance of instinct 
is concerned. Discriminate isolation has been called by 
Gulick segregate breeding, and indiscriminate isolation sepa- 
rate breeding. 

Now the effectiveness of discriminate isolation or segre- 
gate breeding, however effected, to produce species-differ- 
entiation is of course obvious. In fact, as Romanes points 
out, it is only when assisted by some form of discriminate 
isolation which determines the exclusive breeding of like 
with like, that heredity can make in favour of change of 
type or lead to what we understand by organic evolution. 
But what about indiscriminate isolation? Does it not seem, 
at first sight at least, that this kind of isolation must count 
for nothing in the process of evolution? Is it not apparently 
self-evident that the farmer who separated his stock into two 
or more parts indiscriminately, would not effect any more 





OTHER THEORIES OF SPECIES-FORMING, 251 


change in his stock than if he had left them all to breed 
together ? 

“Well,” says Romanes, “although at first sight this seems 
self-evident, it is in fact untrue. For, unless the individuals 
which are indiscriminately isolated happen to be a very large 
number, sooner or later their progeny will come to differ 
from that of the parent type, or unisolated portion of the 
previous stock. And, of course, as soon as this change of 
type begins, the isolation ceases to be indiscriminate: the 
previous apogamy [indiscriminate isolation] has been con- 
verted into homogamy [discriminate isolation], with the 
usual result of causing a divergence of type. The reason 
why progeny of an indiscriminately isolated section of an 
originally uniform stock—e. g., of a species—will eventually 
deviate from the original type is, to quote Mr. Gulick,”* as 
follows: ‘No two portions of a species possess exactly the 
same average character, and, therefore, the initial differ- 
ences are for ever reacting on the environment and on each 
other in such a way as to ensure increasing divergence as 
long as the individuals of the two groups are kept from 
intergenerating.”’ 

Gulick was led to his recognition of the principle in ques- 
tion, not by any deductive reasoning from general principles, 

nities Dut by his own particular and detailed observa- 
iesof Hawaiian tions of the land mollusca of the Sandwich 
land-snails.  Tslands. Here there is an immense number 
of varieties belonging to several genera; but every variety 
is restricted, not merely to the same island, but actually 
to the same valley. Moreover, on tracing this fauna 
from valley to valley, it is apparent that a slight varia- 
tion in the occupants of valley 2 as compared with those 
of the adjacent valley 1, becomes more pronounced in 
the next valley 3/ still more so in 4, etc.,.etc.. Thus it 
was possible, as Mr. Gulick says, roughly to estimate the 
amount of divergence between the occupants of any 


252 DARWINISM TO-DAY. 


two given valleys by measuring the number of miles be- 
tween them. 

On the basis of his detailed observations, Gulick*® has 
proposed the following three general propositions as to the 
relations of isolation to species-forming : 

“1. A species exposed to different conditions in the differ- 
ent parts of the area over which it is distributed, is not 
represented by divergent forms when free inter-breeding 
exists between the inhabitants of the different districts. In 

, /other words, diversity of natural selection without separation 
‘| does not produce divergent evolution. 

“2, We find many cases in which areas, corresponding in 
the character of the environment, but separated from each 
other by important barriers, are the homes of divergent 
forms of the same or allied species. 

“2. In cases where the separation has been long continued, 
and the external conditions are the most diverse in points 
that involve diversity of adaptation, there we find the most 
decided divergences in the organic forms. That is, where 
separation and divergent selection have long acted, the re- 
sults are found to be the greatest. 

“The first and second of these propositions will probably 
be disputed by few, if by any. The proof of the second is 
found wherever a set of closely allied organisms is so dis- 
tributed over territory that each species and variety occu- 
pies its own narrow district, within which it is shut by bar- 
riers that restrain its distribution, while each species of the 
environing types is distributed over the whole territory. 
The distribution of terrestrial molluscs on the Sandwich 
Islands presents a great body of facts of this kind.” 

Finally in a recent exhaustive discussion of the subject *’ 
of the relation of isolation to evolution Gulick declares that 
“the whole process of bionomic evolution, whether progres- 
sive or retrogressive, whether increasingly ramified and 
divergent, or increasingly convergent through amalgama- 


OTHER THEORIES OF SPECIES-FORMING., 253 


tion, is a process by which the limitations of segregate breed- 
ing are either set up and established or cast down and 
obliterated.” 


APPENDIX. 


* Seebohm, Henry, “Physiological Selection,” p. 12, 1886. 

? Romanes, G. J., “Darwin and After Darwin,” Vol. III. p. 1, 1897. 

* Wagner, Moritz, “Die Entstehung der Arten durch Raumliche 

Referencesto onderung,” 1889. This book is made up of the 
discussions of collected papers of Wagner, printed originally in the 
isolation. time from 1868-1886, mostly in the journal Kosmos. 

* Wagner, Moritz, “Uber den Einfluss der geographischen Isolie- 
rung und Kolonienbildung auf die morphologischen Veranderungen 
der Organismen,” July, 1870. 

* Wagner, Moritz, “Uber die Entstehung der Arten durch Abson- 
derung,”’ Kosmos, 1880. 

*Haacke in his “Grundriss der Entwicklungsmechanik,” 18097, 
gives, on pp. 335-330, an excellent summary statement of Wagner’s 
position, as follows: 

“Wenn wir eine Tierart bis an die Grenze ihres Verbreitungs- 
gebietes verfolgen und diese Grenze tiberschreiten, so stossen wir 

Haacke’ssum- gewOhnlich sehr bald, und oft schon, ehe wir die 
mary of Wag- Verbreitungsgrenze der betreffenden Art  erreicht 
ner’s theory, haben, auf eine andere, und zwar auf eine mit der 
ersteren nachstverwandte Tierart, die aber ein anderes Verbreitungs- 
areal inne hat. Gehen wir auch uber das Gebiet dieser letzteren 
Art hinaus, so kOnnen wir auf eine dritte, vierte und ftinfte Art 
stossen, von denen jede den beiden ersten verwandt sein kann und 
ein besonderes Verbreitungsgebiet bewohnt. Im allgemeinen kon- 
nen wir den Satz aufstellen, dass es keine zwei nachstverwandten 
Tierarten giebt, deren Verbreitungsgebiete sich vollkommen decken. 
Vielfach kann der Fall festgestellt werden, dass die Verbreitungsge- 
biete zweier nachstverwandter Tierarten sich teilweise decken; aber 
eine vollkommene Deckung ist noch in keinem Fall bei zwei oder 
mehr nachstverwandten Tierarten festgestellt worden. Es kann 
auch vorkommen, dass das Verbreitungsgebiet der einen Art voll- 
standig innerhalb desjenigen der andern Art liegt, das also, soweit 
der Wohnkreis der ersten Art reicht, ein Zusammenfallen mit dem 
Verbreitungsgebiet der zweiten Art stattfindet; aber in solchen 
Fallen dehnt sich eben die Heimat der einen Art ttber die der 
zweiten aus, so dass von Kongruenz der beiderseitigen Wohnge- 
biete nicht die Rede sein kann. Nachtsverwandte Tierarten sind 


254 DARWINISM TO-DAY. 


ketten- oder, besser gesagt, netzformig tiber die Erde verbreitet. 
Wie die Maschen eines Netzes reihen sich die Wohngebiete der 
Arten einer Gattung aneinander, und wenn auch, wie schon hervor- 
gehoben, mancherlei teilweise Deckungen vorkommen, so hat sich 
noch in allen Fallen, wo man die Grenzen der Verbreitungsgebiete 
nachstverwandter Arten festgestellt hat, die Thatsache ergeben, dass 
keine vollkommene Deckung stattfindet. Aus dieser Thatsache 
konnen wir den Schluss ziehen, dass in einem und demselben 
Gebiete, soweit wenigstens alle Individuen unter denselben Ver- 
haltnissen leben, aus einer Art nicht zwei oder mehr neue Arten 
werden kénnen. Wagner meinte zuerst, dass hierbei die Moglich- 
keit einer allseitigen Kreuzung, wie sie nach ihm innerhalb eines 
und desselben Wohnkreises einer Art moglich sein soll, eine grosse 
Rolle spielt. Er hat ibrigens seine Ansichten im Laufe der Zeit 
geandert und es ist deshalb notwendig, auf die Entwickelungs- 
geschichte seiner Ideen etwas naher einzugehen. Urspriinglich 
suchte Wagner seine Theorie mit der Darwin’schen zu vereinigen. 
Nach der letzteren entsteht eine neue Art dadurch aus einer 
vorhandenen, dass die Lebensbeeinflussungen andere werden, und 
dass nunmehr diejenigen Individuen seitens der ztichtenden Natur 
ausgewahlt werden, die den neuen Lebensbeeinflussungen am 
besten entsprechen. Wagner nahm nun an, dass dies zunachst nur 
einzelne Individuen sein konnen, und dass nicht bloss sie, sondern 
noch eine grosse Anzahl anderer leben bleiben, so dass nicht allein 
die Moglichkeit, sondern auch die hohe Wahrscheinlichkeit gegeben 
ist, dass die den neuen Lebensbeeinflussungen am besten ent- 
sprechenden, von den ubrigen Individuen der betreffenden Organis- 
menart abweichenden Vertreter der letzteren sich mit denjenigen 
geschlechtlich mischen, die nicht in zweckentsprechender Weise 
abgeandert sind, wodurch die neuen Errungenschaften wieder 
verloren gehen sollten. Wagner suchte also den Nachweis zu 
fiihren, dass die Darwinische Selektionstheorie nicht geeignet sei, 
eine Ziichtung neuer Tier- und Pflanzenarten ohne eine Hilfslehre, 
die er in seiner ‘Migrationstheorie’ gefunden zu haben glaubte, 
nachzuweisen. Er meinte, dass die vorteilhaft abgeanderten 
Individuen, wenn nicht in allen, so doch in manchen Fallen auswan- 
dern wiirden in eine Gegend, wo die Art, der sie angehoren, nicht 
vertreten, wo also die Moglichkeit einer Kreuzung mit unabgean- 
derten Individuen ausgeschlossen ist. Spater hat Wagner seine 
Migrationstheorie durch die der Separation oder der raumlichen 
Sonderung ersetzt, indem er zugleich die Verquickung seiner 
Anschauungen mit denen des Darwinismus zurticknahm. Nach 
Wagners Separationstheorie bilden sich neue Arten dadurch, dass 
auf die eine oder andere Weise etliche Individuen einer Art in ein 


OTHER THEORIES OF SPECIES-FORMING. 255: 


Gebiet :gelangen, das vorher nicht von dieser Art bewohnt war. 
Die Entstehung neuer Arten erklart sich dann nach Wagner 
dadurch, dass, da die Individuen einer Art ja alle mehr oder 
minder voneinander abweichen, die wenigen Grunder der neuen 
Art ihre Besonderheiten bewahren und nicht durch Kreuzung mit 
anderen Individuen wieder einbussen wurden. Die Anpassung 
lasst Wagner aber im Sinne Lamarcks zustande kommen, und 
neben Einrichtungen, die den Organismen von Nutzen § sind,. 
erkennt er andere an, die lediglich der Ausdruck eigenttimlicher 
Struktur sind. Die klimatischen Verhaltnisse sind nach Wagner 
von sehr untergeordneter, die Verhinderung der Kreuzung ist 
von ausschlaggebender Bedeutung. Wagner huldigte ferner der 
Anschauung, dass die weisse Farbe der Polar- und die gelbe der 
Wistentiere dadurch zustande gekommen ist, dass entsprechend' 
gefarbte Individuen von Arten, die andere Gegenden bewohnten,. 
nach den Polarlandern und den Wisten auswanderten.” 

‘Jordan, D. S., “The Origin of Species through Isolation,” 
Science, N. S., Vol. XXII, pp. 545-562, 1905. 

* An excellent example of the careful study of the relation of a. 
group of recognised varieties, or sub-species of a species, to the 

Grinnell’s study Climatic differences of their various geographic 
of geographic ranges, is presented by Jos. Grinnell in ‘The Origin 
differences in the and Distribution of the Chestnut-backed Chickadee,” 
chickadee, Auk, Vol. Il, pp. 364-382, 1904. I quote from this: 
paper the following: 

“The chestnut-backed chickadee (Parus rufescens) is a boreal. 
species of peculiarly limited distribution. It is almost exclusively 
confined to the humid Pacific Coast region of North America, 
within which it is the most abundant, and in many places the 
only member of the genus Parus present. We find it characteris- 
tically at home within the densest coniferous forests, or along their 
edges; where there is much shade and an even temperature. 

“The range of the chestnut-backed chickadee is nearly two 
thousand miles long, north and south, extending from a little north 
of Sitka, Alaska, to some forty miles below Monterey, California. 
But its width is very narrow, only within the confines of Oregon 
and Washington exceeding one hundred miles, and elsewhere 
usually much less, save for one or two isolated interior colonies. 
to be mentioned later. 

“The influences determining this queer-shaped distribution area 
may be safely assumed to be atmospheric humidity, with associated 
floral conditions. For this habitat coincides quite accurately with 
the narrow coastal belt of excessive cloudy weather and rainfall. 

“The specific character distinguishing Parus rufescens from all. 


256 DARWINISM TO-DAY. 


other American chickadees is the colour of the back, which is an 
intense rusty-brown, approaching chestnut. It is of common note 
that the most evident effects of similar climatic conditions on other 
animals is a corresponding intensification of browns, especially 
dorsally. We may, therefore, consider the chestnut-backed chicka- 
dee, as indicated by its chief specific character, to be a product 
exclusively of the peculiar isohumic area to which we find it 
confined. 

“Parus rufescens, from Sitka to Monterey, has a chestnut-coloured 
back. And from Sitka to Point Arena, between which we find 
the extremest humidity, another conspicuous character is uniform,— 
the colour of the sides, which are also deep rusty brown. But from 
Point Arena south to San Francisco Bay (Marin District), these 
lateral-brown areas suddenly weaken to pale-rusty; while from 
San Francisco south past Monterey (Santa Cruz District), adult 
birds have the sides pure smoke-gray without a trace of rusty. 

“The species thus presents geographic variation within itself, and 
three distinguishable forms have been named, respectively, the chest- 
nut-sided chickadee (Parus rufescens rufescens), the Marin chick- 
adee (Parus rufescens neglectus), and the Santa Cruz chickadee 
(Parus rufescens barlowi). But all three sub-species are unmis- 
takably the chestnut-backed chickadee (Parus rufescens).... 

“As has already been asserted, Parus rufescens doubtless arose 
as a geographical race of Parus pre-hudsonicus [the hypothetical 
common ancestor of the present species, Parus hudsonicus, occupy- 
ing the interior of Alaska and British Columbia east to Labrador 
and Nova Scotia, and Parus rufescens]. It is now called a ‘species’ 
because intermediates have dropped out; in other words, the 
divarication is now wholly complete and there are two separate 
twigs. The area of intermediate faunal conditions between the 
humid coast belt and the arid interior region of British Columbia 
and Alaska is very narrow, consisting, in places personally 
traversed by me, of but a few miles over a mountain ridge. This 
very narrowness of the area of faunal mergence probably accounts 
for the lack of intermediates at the present day between hudsonicus 
and rufescens. 

“In the case of Parus rufescens and Parus hudsonicus, there 
seems to be now a narrow hiatus between the two. At least I can 
find no record of the two species having been found in the same 
locality. The narrowness of the region of intermediate faunal 
conditions may therefore be considered as the reason why we do 
not find connecting links between hudsonicus and rufescens at the 
present time. For the amount of difference between these two 
chickadees does not strike me as any greater than, for instance, 


OTHER THEORIES OF SPECIES-FORMING. 257 


between Melospiza cinerea montana and Melospiza cinerea rufina, 
between which there is continuous distribution and free interoscula- 
tion. But we cannot expect any two species of birds or other 
animals to present the same degrees of differentiation in the same 
length of time or’under the same conditions, much less under 
different conditions. For in no two animals is the physical organ- 
isation, in all respects, exactly the same. 

“In a given aggregation of individuals constituting a new colony, 
a certain amount of time is necessary for the set of environmental 
factors to become operative in bringing about new _ inheritable 
characters to a degree perceptible to us. Then the inherited effects 
of invasion and cross-breeding from season to season from the 
adjacent parent centre of differentiation will be evidenced less and 
less, as time elapses, as the distance from this centre increases. 
The offspring of successively further removed unions will, of course, 
inherit to a less and less degree the distinctive characters of the 
ancestral stock on one side and more and more of the incipient 
ones on the other. 

“If, now, the distance is great enough to permit of the time 
required for adaptive manifestations to become innate, then we 
would find new characters making their appearance distally nearest 
the new centre of differentiation. If the distance were too short 
we would not find new characters showing themselves because 
they would be constantly crowded down by the influx of the old. 
The time factor may, therefore, be reduced by the intervention of 
an impassable barrier. As an instance, we find three (and there 
are probably two other) insular forms of the song sparrow within 
a limited distance among the Santa Barbara Islands, while through 
the same distance on the adjacent mainland there is but one. Or, 
in the case of continuous distribution, the time element may be 
comparatively lessened by the great distance between the range 
limits, and it may be still further decreased as these limits lie in 
faunal areas of more emphatically different nature. The horned 
larks, as well as song sparrows, furnish us several good examples 
of the latter two rules. 

“Tt is isolation, either by barriers or by sufficient distance to 
more than counterbalance inheritance from the opposite type, that 
seems to me to be the absolutely essential condition for the differ- 
entiation of two species, at least in birds. 

“A strong argument in support of this conviction is that we 
never find two ‘sub-species’ breeding in the same faunal area, and 
no two closely similar species, except as can be plainly accounted 
for by the invasion of one of them from a separate centre of 
differentiation in an adjacent faunal area. An appropriate instance 


258 DARWINISM TO-DAY. 


in illustration of the latter is the occurrence together, in the Siski- 
you Mountains of northern California, of the brown Parus rufescens 
of the wet coastal fauna and the gray Parus gambeli of the arid 
Sierran fauna. (See Anderson and Grinnell, Proc. Ac. Nat. Sc., 
Phila., 1903, p. 13.) The Siskiyou Mountains occupy a line of 
mergence between the two faune, and the two respectively repre- 
sentative chickadees have evidently extended their ranges toward 
each other until now over this one small area they occupy com- 
mon ground. Several parallel cases could be cited; their signifi- 
cance seems obvious. 

“We come now to consider the origin of the races of Parus 
rufescens. In a species of recent arrival into a new region (by 
invasion from a neighbouring faunal area), as it adapts itself better 
and better to its new surroundings, granted the absence of closely- 
related or sharply-competing forms, its numbers will rapidly 
increase. This means that there will be increased competition within 
the species itself, on account of limited food supply. The alterna- 
tive results are either starvation for less vigorous individuals 
during recurring seasons of unusual food scarcity, or dissemination 
over a large area. In a way the first might be considered as bene- 
ficial in the long run, as doubtless leading to the elimination of 
the weaker; such a process evidently does take place to a greater 
or less degree all the time, and is important for the betterment of 
the race. But as a matter of observation Nature first resorts to 
all sorts of devices to ensure the spreading of individuals over all 
inhabitable regions; in other words, the extremest intra-competi- 
tion does not ensue until after further dissemination is impossible. 
In birds we find a trait evidently developed on purpose to bring 
about scattering of individuals. This is the autumnal ‘mad im- 
pulse’ which occurs just after the complete annual moult, when 
both birds-of-the-year and adults are in the best physical condition, 
and just before the stress of winter food shortage. Even in the 
most sedentary of birds, in which no other trace of a migratory 
instinct is discernible, this fall season of unrest is plainly in evi- 
dence. I may suggest, not unreasonably, that autumnal migration 
may have had its origin in such a trait as this, the return move- 
ment in the spring becoming a necessary sequence. (See Loomis, 
Proc. Cal. Acad. Sc., 3d series, Zodlogy, II, Dec., 1900, 352.) It 
is a matter of abundant observation that autumn is the season when 
we find the most unlooked-for stragglers far out of their normal 
range and when sober, stay-at-home birds, like Pipilo crissalis and 
the chickadees, wander far from the native haunts where they so 
closely confine themselves the rest of the year. It is also the expe- 
rience of collectors that the greatest number of these stragglers 





OTHER THEORIES OF SPECIES-FORMING. 25y 


are birds-of-the-year, which thus, obeying the ‘mad impulse,’ are 
led away from their birthplace into new country, where they may 
take up their permanent abode, and be less likely to compete with 
their parents or others of their kind. Then, too, cross-breeding 
of distinctly related individuals is more likely. The records of 
the Santa Cruz chickadee outside of its regular breeding range, are 
all of August to October dates (Haywards, Gilroy, San José, etc.). 

“Thus, as above indicated, by the occupancy of new territory 
the number of individuals which can be supported will corre- 
spondingly grow. Hence a vigorous colony will spread out along 
lines of least resistance, being hindered by slight faunal changes, 
but completely checked only by topographic or abrupt climatic 
barriers. Parus hudsonicus and its near relative Parus rufescens 
are boreal species, the former inhabiting the Hudsonian Zone and 
the latter a certain portion of the Canadian. It seems reasonable 
to suppose that rufescens differentiated in the northern part of the 
humid coast belt, which has been called the Sitkan District. This 
is a faunal subdivision of the Canadian Zone, and its northern 
part approximates more closely Hudsonian conditions than south- 
erly. Granting that the early centre of differentiation and distri- 
bution of Parus pre-hudsonicus rufescens was in the northern part 
of the Sitkan District, then the route of emigration would be con- 
fined to the narrow southward extension of that faunal area. The 
habitat of Parus rufescens thus gradually acquired the long north 
and south linear appearance, as shown at this day. But when the 
pioneer invaders at the south reached the vicinity of Point Arena, 
they met with somewhat changed temperature and consequent 
floral conditions, but not so abrupt as to constitute a permanent 
barrier. Doubtless the progress of invasion was retarded until 
adaptive modifications evolved, which correlatively allowed of 
further invasion, until the abrupt limits of the Santa Cruz Dis- 
trict were reached. 

“San Francisco Bay and the Golden Gate seem to now form a 
pretty effectual barrier between neglectus on the north and barlowi 
on the south. At least, among the large number of skins examined 
by me with this point in view, I can find none from one side that 
can be confidently determined as being identical with the race on 
the other. Neither chickadee has been found east of the bay, nor 
anywhere nearly so far from the coast belt, except for one record 
of a specimen taken in the fall at Haywards. This has been reéx- 
amined and proved to be barlowi, as was to be expected from its 
contiguity. However, the Golden Gate. is so narrow that an occa- 
sional crossing may take place. This was more probable formerly, 
when the redwood timber grew up to the Gate on both sides. 


260 DARWINISM TO-DAY. 


Heermann, in 1853, recorded the species from ‘San Francisco.’ But 
now, I think, the bird is unknown for several miles on either side 
of the Gate. Doubtless this barrier accounts in part for the 
origin of the distinct form barlowi within so short a distance... . 

“As has become a generally accepted idea, the young plumages of 
birds, if different at all from those of the adults, present a gener- 
alised type of coloration; or, to express it in another way, the 
young more nearly resemble recent ancestral conditions. The 
familiar examples of the spotted, thrush-like plumage of the young 
robin and the streaked, sparrow-like plumage of young towhees 
and juncos are cases in point. Accepting this phylogenetic signifi- 
cance of ontogeny, we find the chickadees giving some interesting 
illustrations. 

“Although the adult of barlowi has the sides pure smoke-gray, 
the juvenal plumage possesses pale-rusty sides. This points 
towards a rusty-sided ancestor like neglectus. This also agrees 
perfectly with the distributional evidence of origin. The adult of 
neglectus has pale-rusty sides; the young also has rusty sides, but 
somewhat darker than in the corresponding age of barlowi, and 
moreover is more nearly like the juvenal plumage of rufescens. 
But the sides in adult rufescens are deep brown, almost chestnut, 
while the young has much paler, merely dark-rusty sides. And 
what is most significant is that the young of rufescens and hud- 
sonicus are much nearer alike than are the adults, the former hav- 
ing only very slightly darker rusty on the flanks. The young of 
hudsonicus in respect to intensity of browns almost exactly equal 
the adults of the same species, showing that the present coloration 
is of very long standing, and offering further evidence that hudson- 
icus is nearest the common stock form of all the chickadees under 
consideration. Juvenal characters, resembling ancestral conditions, 
lag behind the newer acquired adult characters. 

“To repeat: The young of barlowi has the sides paler rusty than 
neglectus, neglectus slightly paler than rufescens, but rufescens has 
the sides slightly more rusty than hudsonicus, a sequence which 
accords well with the present theories of origin.” 

* Kellogg, V. L., ‘““New Mallophaga, I,’’ Contrib. to Biol. from the 
Hopkins Seaside Laboratory of Leland Stanford Jr. University, 
1896. 

** Smith, Jas. P., “Studies for Students: Geological Study of 
Migration of Marine Invertebrates,” Journal of Geology, Vol. III, 
Pp. 481-495, 1895. 

** Any selective breeding or segregation produced by other means 
than the separation of groups of individuals by actual topographic, 
or geographic barriers may be called biologic or sexual isolation. 


OTHER THEORIES OF SPECIES-FORMING. 261 


1? Plate, L., “Uber die Bedeutung des Darwin’schen Selections- 
prinzip,” p. 193, 1903. 
** Hutton, F. W., “The Place of Isolation in Or- 


Purther refer- panic Evolution,” Nat. Science, Vol. XI, pp. 240-246, 
ences to discus- 


sions of isolation, 1897- ; ; : 
** The not uncommon mating, in zoological gardens, 


of lions and tigers, with the production of healthy cubs, is a case 
in point. 

*® This principle, strongly advocated by Romanes, seems first to 
have been presented by Eimer in connection with his theory of 
orthogenetic evolution. At least it enters into the make-up of the 
Eimerian theory. See account of Eimer’s theory in chapter x of this 
book. | 

** Jordan, Karl, “‘Mechanische Selection,” 1896; see also Peter- 
sen, Wilh., ““Entstehung der Arten durch Physiologische Isolirung,” 
Biol. Centralbl., Vol. XXII, pp. 468 ff., 1902; also Vol. XXIV, pp. 
423-431, 467-473, 1904. Author describes cases of marked differ- 
ence in reproductive organs (includes primary and accessory parts) 
of closely allied species of Lepidoptera. 

*7 Snodgrass, R. E., “The Terminal Abdominal Segments of 
Female Tipulide,” Jour. N. Y. Ent. Soc., Vol. XI, pp. 177-183, 1903; 
“The Hypopygium of the Tipulide,” Trans. Amer. Ent. Soc., Vol. 
XXX, pp. 179-235, 1904; ‘“The Hypopygium of the Dolichopodide,” 
Proc. Cal. Acad. Sct., Ser. 3, Zool., Vol. II], pp. 273-285, 1904. 

*® Seebohm, H., “Physiological Selection,” 1886. 

** Wallace, A. R., “Darwinism,” p. 180, 1891. 

*° Jordan, Karl, ‘““Novitates Zoologice,” pp. 426 ff., 1896. 

“Vernon, H. N., “Reproductive Divergence: An Additional 
Factor in Evolution,” Natural Science, Vol. XI, pp. 181-189, 1897. 

*? Jordan, Karl, “‘Reproductive Divergence: A Factor in Evolu- 
tion?” Natural Science, Vol. II, pp. 317-320, 1897. 

*® Pearson, Karl, ‘“Reproductive Selection,” Natural Science, Vol. 
VIII, pp. 321-325, 1806. 

** Romanes, G. J., “Isolation in Organic Evolution,” Monist, Vol. 
VIII, pp. 19-38, 1897. 

*° Gulick, J. T., “Divergent Evolution through Cumulative Segre- 
gation,’ Jour. Linn. Soc., Zool., Vol. XX, pp. 189-274, 1888. 
Slaiiick, = lobo J Ours Linn. SdC..> 2001, Vol. XX... pp: 202-211, 
1888. 

*7 Gulick, J. T., “Evolution, Racial and Habitudinal,” Pub. No. 
25, Carnegie Institution of Washington, 1905. In this large paper 
are to be found references to all of the author’s important papers. 
Some of these papers are reprinted (some completely, some in 
part) in this monograph. 


CHAPTER Xe 


OTHER THEORIES OF SPECIES-FORMING AND 
DESCENT (CONTINUED): THEORIES ALTER 
NATIVE TO SELECTION. 


WE come now to the brief consideration of three general 
theories, or groups’ of theories, which are offered more as 
alternative or substitutionary theories for natural selection 
than as auxiliary or supporting theories. These groups of 
theories are the Lamarckian one, based on the inheritance 
of characters acquired individually (ontogenetically) during 
the lifetime of the organism due to the effects of use and 
disuse and functional stimuli; the general conception of 
orthogenesis variously provided for by Nageli, Eimer, 
Jaeckel (metakinesis), and others, and finally the theory of 
heterogenesis, suggested by von Kolliker, definitely formu- ° 
lated by Korschinsky, and most recently, and importantly, 
developed by de Vries. Few biologists would hold any of 
these theories to be exclusively alternative with natural 
selection; de Vries himself would restrict natural selection 
but little in its large and effective control or determination 
of the general course of descent. But all of these theories 
offer distinctly substitutional methods of species-forming, 
and one of them includes certainly the most favoured expla- 
nation, next to selection, of adaptation, while the authors or 
later up-holders of some of them actually deny any con- 
structive, that is, adaptational, species-forming or descent- 
controlling, influence of natural selection. 

The Lamarckian Theory.—Iit is a great presumption to 
attempt to offer in so small a book as this any exposition of 
a theory so long known and elaborately developed as the ex- 

262 


OTHER THEORIES OF SPECIES-FORMING. 263 


planation of adaptation and species-forming known as La- 
marckism. Lamarck* proposed his theory at 
a time most inopportune; it met with no gen- 
eral acceptance, but in later years, post-Darwinian years, 
fair-minded biologists have turned back to the books and 
papers of this pioneer French exponent of the evolution 
principle and have given his theory the careful attention and 
scrutiny it deserves—but which it failed to get from 
Lamarck’s contemporaries. This reéxamination of the La- 
marckian theory or theories has given rise to most radically 
divergent opinion and belief concerning its worth: many 
biologists account it of great value, others reject it prac- 
tically in toto. But this acceptance or rejection depends 
almost entirely on one’s attitude toward a single funda- 
mental part of it, namely, the assumption that variations, | 
modifications, or characteristics acquired during the life- | 
time of an individual, these modifications usually being due | 
to use, disuse, or other functional stimulation of organs and | 
parts, can be transmitted by this individual to its offspring. © 
If such newly-acquired, non-inherited characteristics can be 
transmitted in full and in detail, or even approximately so, 
from the parent to the young, then Lamarckism obviously 
offers the simplest of all the explanations so far presented, 
of nearly all active and of many passive adaptations. lf 
such characters cannot be so transmitted, then Lamarckism, 
as plausible, as reasonable, as simple and effective as it 
seems to be, is practically without validity. 

Now this matter of the inheritance of acquired charac- 
ters, apparently easily susceptible of definite proof or refuta- 

Thorton by observation and experiment, has been 
of acquiredchar- for years and is to-day one of the burning prob- 
rig lems of biology. There is no general agree- 
ment about it, no consensus of authority even. Just at pres- 
ent the weight of evidence inclines strongly against such 
an inheritance, chiefly because of Weismann’s successfully 


Lamarckism. 


Pa 


204 DARWINISM TO-DAY. 


destructive criticism of about all the evidence of observa- 
tion which has been offered in behalf of it. And yet just at 
the present time do biologists recognise more keenly than ever 
the need and relief the actuality of such inheritance would 
give them in their attempts to solve the great problems of 
adaptatioh and species-forming? I cannot undertake to say 
whether more reputable biologists disbelieve in than believe 
in the existence of such inheritance, but it is obvious that 
the disbelievers have the present prestige of apparent vic- 
tory: they call for convincing evidence of such inheritance, 
and it is not produced. On the other hand, there are many 
reputable, thoughtful, honest, actively working biologists and 
paleontologists (particularly many paleontologists in pro- 
portion to the total number of palzontological students) who 
say, although not loudly and even a bit shamefacedly, per- 
haps, that they must believe in the possibility and the actu- 
ality of this inheritance; there is no getting forward with- 
out it. 

In taking up our brief exposition of Lamarckism, let me 
say first that only in post-Darwinian years has Lamarckism 
been put so strongly in contrast with Darwinism as it has. 
Darwin himself included part of Lamarckism as a minor 
factor or influence in his explanation of adaptation and 
species-forming, and Plate, in the recent most notable criti- 
cal discussion of Darwinism, takes nearly exactly the old 
ground of Darwin, namely, an acceptance of the inheritance, 
in some degree and under some conditions, of acquired 
characters, and the consequent possibility of a certain 
amount of Lamarckian orthogenesis, 7. e., an orthogenesis 
due to the inheritance of the results of use, disuse, and func- 
tional stimuli. It is only neo-Darwinism (of Weismann, 
Wallace, and others) and neo-Lamarckism (of Spencer, 
Packard, and others) that are so radically opposed, so mutu- 
ally exclusive. 


/ That an animal in its lifetime, and especially during its 


OTHER CTHEORIES (OF *SPECIES-FORMING, 265 


immature life can effect very considerable changes in some 

The concep- Of its body-parts by special use or disuse of 
Sauna these parts, or that certain parts may be modi- 
Lamarck, fed through the influence of external stimuli, is 
familiar knowledge. Let one recall the increase of the 
blacksmith’s biceps and inversely the degeneration of un- 
used muscles, and the thickening or callousing of palms or 
other parts of the skin exposed to repeated rough contact.. 
Bones have ridges developed on them by repeated muscle-: 
pulls, the hands and eyes can be trained to special functional 
skill which involves important although perhaps slight physi- 
cal changes, the heart and lungs can be enlarged by special 
use; in short, almost any of the organs of the body, which 
are actively used, can be modified either by unusual or extra 
use, or by unusual lack of use. Now this use is, in Nature, 
almost always of the character of a better aiding in success- 
ful living; that is, it is adaptive use. Animals often chased 
by enemies become fleeter by practice; animals that must 
dig for roots or climb trees for leaves and fruits, or dive for 
fishes, or leap over obstacles, come by repeated digging, climb-. 
ing, diving, or leaping to do these things better ; the muscles 
and tendons and bones work together better and _ better, 
become physically modified in accordance with these endeav- 
ours. If such betterment of organs and their functions. 
acquired by individuals could be inherited by their young, 
it is obvious that general adaptations of this sort could be 
rapidly developed in the course of generations, and new 
species, new, that is, because of the adaptive changes thus 
elected, be formed. »* This? is the essential thought in 
Lamarck’s theory of the method of adaptation and species- 
forming. In almost all criticisms of Lamarckism one reads 
much contemptuous reference to the expected results of the 
organism’s “willing” to vary or change in this or that direc- 
tion. As a matter of fact the critics of Lamarckism give 
that rather absurd feature of alleged Lamarckism much 


266 DARWINISM TO-DAY, 


more conspicuousness than Lamarck did. He did, indeed, 
make some reference to the possible volitional effort of the 
organism to change along certain desirable lines, but it is 
evident that Lamarck had more in mind the animal’s desires 
and needs to stretch up higher for leaves or to dig better or 
run faster, leading to actual attempts to do these things, than 
to any expected results of mere mental wishing or willing. 
\The essential principle of Lamarckism is an orthogenetic 
levolutionary progress toward better and finer adaptation and 
adjustment resulting from the inherited effects of actual use, 
‘disuse, and functional stimulation of parts. It is a great 
thought and a clear one, and only needs the proof of the 
actuality of the inheritance of individually acquired char- 
acters to make it one of the principal causal explanations 
of adaptation and species change. 

However, it is exactly this proof that is wanting. At any 
rate, proof of the character and extent necessary to con- 

eer ry ce all or even a majority of biologists is 
successful attack Wanting. The examples or cases brought for- 
on Lamarckism. 4rd by Lamarckians of the alleged inheritance 
of mutilations, of the results of disease, and of use and 
disuse, are not convincing. It is one of Weismann’s posi- 
tive contributions to biology to have analysed case after 
case of alleged inheritance of acquired characters, and shown 
its falseness or at least uncertainty. Many of these cases 
he has been able to explain as a result of selection; others 
remain inexplicable; a few,’ only, are insisted on by the 
Lamarckian champions as indisputable examples of such 
inheritance. But this very paucity of so-called proved 
cases, where there should be thousands of obvious ex- 
amples if the principle were really sound, is argument against 
Lamarckism. 

Our knowledge, too, of the mechanism of heredity makes 
strongly against the theory of the inheritance of acquired 
characters. Another of Weismann’s positive contributions 


OTHER THEORIES OF SPECIES-FORMING. 207 


to biology is his generally sound distinction between the 
germ-plasm and the soma-plasm and parts of the many- 
celled body. At maturity the animal body is composed of a 
small mass of germ-plasm (germ-cells) situated in the 
ovaries or testes, and a great mass of somatic tissues and 
organs, all the rest of the body, in fact. Now what is the 
condition that exists in the body after a somatic part is 
modified by use or disuse or by other functional stimulus, as 
when a muscle is enlarged by exercise, the sole of the foot 
calloused by going barefoot, an ear more finely attuned by 
training? We have a definite physical change in a definite 
organ, but is the germ-plasm in any way changed or 
affected by this superficial or specific somatic modification, | 
or if changed is it changed so that it will reproduce in its 
future development a similar change in the same organ of 
the future new individual? What possible mechanism have 
we in the body to produce or insure such an effect on the 
germ-plasm? The answer is obvious and flat; we certainly 
know of no such mechanism; in fact what we do know of 
the relation of the germ-cells to the rest of the body makes 
any satisfactory conception of such a mechanism as yet 
impossible. | 

Not that certain external conditions may not directly 
affect the germ-cells, imbedded and concealed as they are 

<a in the body. he arying conditions of tempera- 
the way of ture,* of humidity, and of magnetism, perhaps, 
tt een certainly anything influencing the food supply 
acquiredchar- and nutrition, can influence the germ-cells at 
seo the same time as it affects all the rest of the 
body. But will this influence photograph on these un- 
_ differentiated cells the same picture that it impresses on the 

* While temperature may be looked on as an extrinsic influence 
affecting germ-cells as well as all other parts of the body, it must be 
kept in mind that warm-blooded animals (birds and mammals) 


regulate the inner temperature of the body. So changes in external 
temperature would but slightly, or not at all, affect the germ-cells. 


\ 


268 DARWINISM TO-DAY. 


affected somatic parts. A high temperature or a moist at- 
mosphere may modify the colour of the skin, change the pat- 
tern of the body superficies, but will overheated germ-cells 
produce new individuals showing the same changes of skin 
colour and pattern if the same conditions of environment of 
the soma are not repeated? How much less conceivable, 
then, is the influencing of the germ-cells so as to compel 
them to reproduce on daughter body-parts specific effects. 
produced on special parental body-parts by such specific and 
localised influences as vigorous use of an arm, disuse of a 
leg muscle, repeated contact of the palm of the hand with 
hard bodies. Indeed, this lack of means of relating the 
germ-plasm to the soma, the rest of the body, has stood 
much in the way of any satisfactory conception of the phe- 
nomena of heredity, that is, the reproduction by the germ- 
cells of new individuals resembling the parental, and kas 
led to constant and thoughtful attention and speculation ever 
since the time of Darwin; indeed, from long before Dar- 
win’s time. 

One of the most favoured ways of attempting to explain 
how the germ-cells can represent in their make-up, and 
possess the capacity to develop into, the whole complex body, 
has been to conceive of the giving off of small representa- 
tive particles from all the cells of the body which should be 
carried by the blood to the germ-plasm and deposited in the 
germ-cells. The germ-cells in their development would 
then, by virtue of this manifold representation, be able to 
expand into the whole body during a shorter or longer 
course of development and growth. This notion of the com- 
position of the germ-plasm of micromeres collected from all 
the somatic cells, is the conception at the basis of Buffon’s 
theory of “organic molecules,’ of Spencer’s “physiological 
units,” Maggi’s “plastidules,’ Altmann’s “‘bioblasts,’”” Wies- 
ner’s “plasomes,” Darwin’s “gemmules,”’ Galton’s “stirps,” 
Nageli’s “micelle,” Weismann’s “biophors and determi- 


OTHER THEORIES OF SPECIES-FORMING. 269 


bP) 


nants,’ and of numerous other micromeric theories.” But 
the facts of budding, especially as exemplified in plants, 
and of regeneration among animals, both of these kinds of 
phenomena seeming to show that germ-plasm is not neces- 
sarily limited to the germ-cells, strictly so-called, have pre- 
vented the acceptance of a too rigorous interpretation of 
Weismann’s distinction between the germ-plasm and the 
soma, and have led to some theories of germ-plasm make-up 
and disposition differing from the ones proposing a rigid 
restriction of germ-plasm to the germ-cells. The facts that 
in many plants any part, as a bit of a twig, say, if cut off, can 
reproduce the whole plant just as effectively as a seed 
germ-cell) can, and that many animals can reproduce con- 
siderable and complex parts, if lost by accident or self-. 
mutilation, show that there often resides in somatic cells of 
much specialisation the capacity to reproduce not only cells 
of their own kind but others of much variety and different 
specialisation. So some biologists believe that there is either 
a net-work of primitive germ-plasm extending throughout 
the soma cells (Nageli’s idioplasm theory for example), or 
that each somatic cell (at least those with the capacity of 
regeneration or reproduction by budding, cuttings, etc.) con- 
tains a little primitive germ-plasm stuff besides its own 
soma-plasm. And some authors have seen in such theories, 
of a widely diffused germ-plasm a mechanism for the trans- | 
mission from the soma to the central germ-cells of the 
effects of use, disuse, and functional stimuli derived from | 
external sources. But does even this conception of a diffuse 
and connected germ-plasm, after all, clear up in any way 
our difficulty? It makes it easier to see how germ-plasm 
may be affected by external and superficial influences, but 
does it explain in any degree how these effects can be car- 
ried to the germ-cells and so stamped on them as to compel i 
them to reproduce photographically in their later develop-|/ 
ment into new individuals, the specific effects that use, dis-” 


270 DARWINISM TO-DAY. 


use, and external stimuli may have had on specific soma 
parts of the parent? 

Indeed, Haacke * well points out that many or most cases 
of apparently direct working of extrinsic influences on the 
body are really indirect, in that these influences 
do not actually directly modify the structure, as 
a blacksmith’s hammer modifies the shape of a 
piece of red-hot iron, or a seal shapes the drop of melted 
wax, but that they do it indirectly as stimuli inducing chemi- 
cal processes, nervous impulses, etc. The adaptive re- 
arrangement of spongy tissue in broken and poorly reset 
long bones, apparently a direct reaction, is really only in- 
direct, occurring through complex chemical processes, 1. @., 
the bringing of special bone-forming materials to certain 
places, etc. The outer influences are all stimuli, not actual 
sufficient causes or manipulations. 

Haacke makes a proposal of much ingenuity, after a keen 
and suggestive discussion of the inheritance of acquired 
characters problem, to explain how such an inheritance may 
be effected. It is based on the fact that no characters are 
directly acquired; that is, that any change is only the result 
of some external stimulus and not of a directly and imme- 
diately moulding cause, and that, therefore, in any phenom- 
enon of stimulus and effect much more of the body substance 
than that composing the exact part or region modified is 
influenced. From this Haacke sees the possibility, even the 
necessity, of a modification of the whole constitution, includ- 
ing the germ-plasm (or perhaps the germ-plasm is modified 
as a result of the modification of the whole constitution or 
body in which the germ-plasm is being developed and 
formed). Thus every acquirement of a new character or 
change in an old one must or may affect the germ-plasm. 
With regard to passive organs such as the chitin skeletal 
parts of insects and crabs, Haacke points out that they are 
only the product of active organs, 1. e., the secreting skin- 


Haacke’s 
discussion: 


OTHER THEORIES OF SPECIES-FORMING., 29% 


cells, etc. Use and disuse are equivalent simply to much or 
little metabolism, and metabolism is as necessary to produce 
passive organs or to change them, as use is to make muscles. 
larger. } 

However, despite the successful destructive criticism by 
Weismann and the neo-Darwinians of the alleged cases of 

Many natura oe inheritance of acquired characters adduced 
ists believein by the Lamarckians, and in spite of our lack of 
the inheritance : ve ‘ 
of acquired knowledge, and indeed, difficulty of conception 
characters. of any mechanism in the body capable of im- 
pressing on the germ-plasm the effects of use, disuse, and 
external stimuli in such a way as to compel a photographic 
reproduction in the young of these effects as manifest in 
the soma of the parent, numerous biologists do not hesitate 
to avow their conviction of the actuality of such inheritance. 
Now these biologists must have some basis of observation or 
scientific fact for their belief. What is this basis? They rest 
their belief largely upon a kind of proof by indirection, a 
certain necessity of consequence of other facts, and a logical 
argument by elimination. The actual observed status of 
animal life to-day and, as revealed by fossils, in past ages, 
which is that of the existence of certain lines of descent or 
evolution obviously following lines of modification based 
on use and disuse; the inadequacy of natural selection to: 
explain the cumulation of adaptive modification until such 
modification shall have reached a life-and-death determin- 


ing selective value; the apparent impossibility of explaining 


the continued degeneration of vestigial organs by natural 


selection; the great difficulty of explaining correlative or 


coadaptive modifications by selection alone; the possibility 
that our lack of knowledge of a mechanism for ensuring the 
hereditary transmission of acquired characters may be over- 
come with further knowledge of the ultimate structure and 
capacity of the germ-plasm; the great reasonableness and 
logical plausibility of the whole Lamarckian conception ;, 


oP keene aber 


a ED i aS ae 


ea bs DARWINISM TO-DAY. 


these and other similarly not wholly convincing reasons are 
the sort of not very admirable scientific evidence that the 
believers in Lamarckism have to stand on. Two groups of 
scientific men are especially well represented among the 
Lamarckians: namely, paleontologists and pathologists, 
(Not all palzontologists’ and pathologists believe in the 
inheritance of acquired characters.) Both of these groups 
are familiar with facts that are unfamiliar to biologists gen- 
erally. And to my mind it is important that biologists should 
recognise the fact that familiarity with the facts of histor- 
ical geology on the one hand and with teratogenesis and 
human disease on the other, seems to lead to a belief in 
Lamarckism.* It should lead the general biologist to be 
less positive in his sureness of the invalidity of Lamarckism. 

But even were the inheritance of acquired characters now 
an established fact, or if it should come to be one, it must 

Lamarckism be kept in mind that Lamarckism could be sub- 
ee aaatte stituted only partly for Darwinism. There are 
tions, many adaptations and much species-forming 
that Lamarckism might explain, but also there are hosts of 
adaptations that Lamarckism cannot explain. © Plate,’ who 
defends natural selection but accepts some part of Lamarck- 
ism, has pointed this out clearly. He asks how the so-called 
“passive adaptations” could be explained by Lamarckism. 
“The salivary glands of a non-poisonous snake could pro- 
duce ever so much saliva, but it would not become poison- 
ous by this, just as little as simple teeth could change by 
use to grooved teeth and these to tubular ones. The tusks 
of Babirussa could not be led to grow through the skin of 
the cheeks through use, for they would have to be actually 

* A scientific man representing another phase of biologic activity, 
and a man who has enjoyed an extraordinary opportunity for the 
observation and testing of modes of inheritance, also believes 
strongly in Lamarckism. This is Luther Burbank, the famous Cali- 


fornia plant-breeder. For some account ° of the scientific aspects of 
Burbank’s work, see the appendix of this chapter. 


OTHER THEORIES OF SPECIES-FORMING. 273 


covered by the flesh for awhile in this process, and during 
this time be incapable of use. With Fierasfer, the fish that 
lives in sea-cucumbers ( Holothurians), the anus lies far for- 
ward in the throat so that the fish has only to thrust its head 
through the anus of the sea-cucumber in order to void its 
feces. How can use of the intestine or its peristaltic move- 
ment have produced such a remarkable change in position 
of the anus?” Plate‘ offers other similar examples of adap- 
tations inexplicable by Lamarckism, and justly says that 
hundreds of others could be adduced. He presents suc- 
cinctly the possibilities of Lamarckism, the inheritance of 
acquired characters being granted, as follows: 

Lamarckism could explain 

(1) many indifferent characters: example, changes of 
temperature produce proportional changes in the 
colour-pattern of butterflies’ wings ; | 

(2) many simple adaptations of active organs: example, 
a muscle becomes stronger through use, and creates 
a crest on a bone through pulls; 

(3) some simple adaptations of passive organs (so-called 
direct adaptations): example, in the whales, the 
water might directly affect the skin and sub-cutane- 
ous tissue and thus produce the loss of hair and the 
layer of fat. 

Lamarckism could not explain 

(1) many characters of active adaptation, even though 
of simple kind: example, the penetrating of the lung- 
sacs of birds through hair-fine holes into all the 
bones ; 

(2) many complicated adaptations of active organs: ex- 
amples, light-making organs, eyes, smelling-organs, 
auditory organs ; 

(3) all complicated passive adaptations: example, mim- 
icry. 

Even if we are ready to admit the possibility or actuality 


274 DARWINISM TO-DAY. 


of the inheritance of acquired characters in some degree or 
under certain conditions—and this partial acceptance has 
always seemed to me no more justified than the flat accept- 
ance of the principle in its entirety; it has seemed a weak 
sort of attempt at compromise with no real basis in reason 
and effecting no advantage in clearing up the problem— 
there can be no acceptance of the all-sufficiency of Lamarck- 
ism as an explanation of adaptation, species-forming, and 
descent, any more than there can be such an acceptance of 
the all-sufficiency of natural selection. Adaptation and spe- 
cies-forming are not, to my mind, one and the same problem: 
adaptation can and does lead to species-forming, but species 


-are formed that are not the results of adaptive modifica- 
_ tion; whose specific characteristics are indifferent; that are, 
| in a word, non-adaptive species. De Vries’s new species of 


a 


evening primroses have a cause not associated with adapta- 
tion. Now Lamarckism certainly cannot explain non- 
adaptive species any better than selection can. Both selec- 
tion and the inheritance of the effects of use, disuse, and 
external stimuli are primarily explanations of adaptations 
and of adaptive species-forming. Lamarckism is, perhaps,. 
through its inclusion of the perpetuation of the direct influ- 
ence of external stimuli, in better condition to explain non- 
adaptive species, but both of these genius-offered explana- 
tions of organic evolution need the aid of another or other 
factors: the unknown factors of evolution, to speak with 
Osborn. | 
Orthogenesis.—One of the principal criticisms of the 
natural selection theory is that of the impossibility of ex- 
jects plaining the beginnings of advantageous modi- 
dence for ortho- fication and the beginnings of new organs, by 
genetic evolution. +e selection of fluctuating individual variation, 
and of explaining the apparent cases of the existence of 
determinate variation and the admitted cases of forthright 
development along fixed lines not apparently advantageous,, 


OTHER THEORIES’ OF SPECIES-FORMING. 275 


| 
| 


and finally of explaining the definite cases of ultra-develop- | 


ment of parts and species beyond the point of advantage even 
to such unfavourable degrees as lead to death and extinction. 
Paleontology * reveals to us the one-time existence of ani- 
mals, of groups of animals, and of lines of descent, which 
have had characteristics which led to extinction. The un- 
wieldiness of the giant Cretaceous reptiles, the fixed habit 
of life of the crinoids, the coiling of the ammonites and 
nautili, the gigantic antlers of the Irish stag—all these are 
examples of development along disadvantageous lines, or to 
disadvantageous degrees. ‘The statistical studies of varia- 
tion have made known numerous cases * where the slight, as 
yet non-significant (in a life-and-death struggle) variation 
in pattern of insects, in dimension of parts, in relative pro- 
portions of superficial non-active structures, are not for- 
tuitous, that is, do not occur scattered evenly about a mean 
or mode according to the law of error, but show an obvious 
and consistent tendency to occur along certain lines, to 
accumulate in certain directions. Many biologists see in 
variation and in species-forming certain determinate char- 
acteristics exhibited by, or lines or paths being followed by 
all or most of the individuals of successive generations ; and 
see in descent certain phenomena of forthright progressive 
movement which they find selection based on utility unable 
to explain. Various theories to account for this apparent 
orthogenetic, but not ortho-selective, development have 
therefore been proposed by biologists, most of which 
theories and most of which biologists are to be looked on as 
antagonistic to the selection theory. For if a theory of ortho-| 
genesis is sufficient to explain those lines of variation and) 
development not explicable by selection, it usually seems to’ 
its maker to be sufficient to explain other lines of evolution. - 
It may very likely occur to some that in speaking of ortho- 
genetic development as contrasted with descent governed by 
selection we are making a distinction without a difference, 


pt A 


276 DARWINISM TO-DAY. 


in that it is obvious that selection also produces ortho- 
genetic evolution, that is, evolution along definite lines; 
that in fact’ it can produce no other kind of 
Orthogenesis evolution. To attribute orthogenetic results to 
contrasted with : . : ; 
orthoselection, Natural selection is quite right, and some one has 
proposed the name orthoselection to distinguish 
orthogenetic evolution as produced by selection from such 
, results produced independently, or at least partly inde- 
ipendently of selection, that is produced in accordance with 
any one or more of the so-called theories of orthogenesis. 
All this latter kind of orthogenesis is distinguished from 
orthoselection in that it presumes all or most of the indi- 
viduals of successive generations to be modified, to vary, 
that is, in a similar manner as a result of factors, intrinsic 
Or extrinsic, producing determinate variation. This is 
plainly different from orthoselection, in which definite lines 
of development are produced by the eradication, through the 
rigour of selective struggle, of all other lines, Variation 
may be wholly fortuitous, miscellaneous, indeterminate ; but 
selection permits only certain kinds of variation to persist, 
to accumulate. In true orthogenesis the variation, and 
hence the lines of modification, are predetermined. It seems 
obvious, however, to any believer in natural selection that 
sooner or later the fate of these lines of development will 
come into the hands of selection. And most orthogenesists 
do indeed admit this. But it is precisely in the making of 
a start in modification that orthogenesis- fills a long-felt 
want, and if capable of proof, should be gladly received by 
Darwinians as an important auxiliary theory in the ex- 
planation of modification, species-forming, and descent. 
The first of these theories of orthogenesis has just been 
») explained, for Lamarckism may be looked on as an expla- 
nation of orthogenetic evolution based on the perpetuation 
‘and accumulation of the effects of use, disuse, and the 
direct effects of functional stimuli. Roux’s battle of the 


OTHER THEORIES OF SPECIES-FORMING. 277 


parts theory, and Weismann’s theory of germinal selection _ 
are also in a way theories of orthogenesis: they explain how | 
variations begin and continue along fixed lines, but they © 
both soon surrender control of descent to natural selection. 
There are, however, two or three theories of 
Different types orthogenesis which have been developed by 
of theories of 
orthogencsisg, their proposers to the degree where they are 
boldly offered as substitutes for: natural selec- 
tion. Two especially notable theories of this character are 
those proposed and defended respectively by Nageli and by 
Eimer. These two are not only the most notable and most 
completely elaborated of orthogenetic theories but they 
represent two radically different points of view among: the 
orthogenesists themselves, in that Nageli found his ortho- | 
genesis-producing factor or cause in a somewhat mystical | 
vitalistic inner force, or so-called Verz vollkomnungsprinzip, 3 
in the organism, while Eimer. finds orthogenesis produced 
and controlled by the directly working. external factors of 
climate, food supply, and environment generally. Similar 
conceptions or beliefs regarding the direct and accumulating 
effect of environmental factors have been presented by Dar- 
win, Haéckel, Cope, Henslow, Emery, Piepers, Lloyd 
Morgan, and numerous others.. In fact probably a majority 
of biologists entertain a conviction—often not clearly de- 
fined and generally unaccompanied by any satisfactory con- 
ception of a mechanism for achieving what they believe 
to exist,—of the actuality of an influence on organic modifi- 
cation and descent directly exerted by those various external 
factors or conditions of organic life which we call, SHIGE 
tively, environment. 
Nageli’s *” theory of orthogenesis depends upon the as- 
sumption of his so-called principle of progressive develop- 
Nageli’s ceney ment (Vervollkomnungsprinsip), a something \ 
of orthogenesis. inherent in the organic world which makes | 
each organism in itself a force or factor making towards | 


278 DARWINISM TO-DAY. 


specialisation, adaptation, that is, towards progressive evo- 
lution. Other authors who accept such a theory of an inher- 
ent driving force in organisms speak of this factor variously 
as an “inner directive force,” an “inner law of development,” 
or an “intrinsic tendency towards progress,” etc. Nageli 
believes that animals and plants would have developed about 
as they have even had no struggle for existence taken place 
and the climatic and geologic conditions and changes been 
, quite different from what they actually have been. Kor- 
schinsky ** says: “In order to explain the origin of higher 
forms out of lower it is necessary to assume in the organism 
a special tendency towards progress.”’ That is, to the be- 
lievers in this kind of a theory of orthogenesis organic 
evolution has been and is now ruled by unknown inner 
forces inherent in organisms, and has been independent of 
the influence of the outer world. The lines of evolution are 
immanent, unchangeable, and ever slowly stretch toward 
some ideal goal. It is needless to say that but few biologists 
confess to such a belief. However much in the dark we 
may be regarding the whole great secret of bionomics, how- 
ever partial and fragmentary our knowledge of the processes 
and mechanism of evolution, such an assumption of a mystic, 
essentially teleologic force wholly independent of and 
dominating all the physico-chemical forces and influences 
that we do know and the reactions and behaviour of living 
matter to these influences which we are beginning to 
/ recognise and understand with some clearness and fulness— 
'such a surrender of all our hardly won actual scientific 
_ knowledge in favour of an unknown, unproved, mystic vital 
| force we are not prepared to make. As Plate well says, such 
a theory of orthogenesis ** is opposed, in sharpest contrast, 
to the very spirit of science. 

On the contrary, the theories of orthogenesis of the 
general type exemplified by Eimer’s ** are directly in line — 
with the spirit of modern biological methods and investiga- 


OTHER THEORIES OF SPECIES-FORMING. 279 


tions; they rest on the assumption that physico-chemical | 
factors produce direct effects on the plastic organism, and 
, anhereree that such effects, repeated and intensified, re- | 
of orthogenetic sult in a certain degree of modification or con- | 
Sue trol of variation and evolution. To be sure, 
there is not yet proposed a very satisfactory mechanism 
for conveying the environmental influence to, and trans- 
lating it into definite effect on the course of development, 
but the obvious fact that environment does strongly affect 
and modify individual function and structure and the rea- 
sonable belief that the modification of the race must ulti- 
mately rest on and proceed from the modification of the 
individual, make the theories of orthogenesis based on en- 
vironmental influence very suggestive and of distinct 
scientific value. In addition, too, there is a certain amount 
of actual evidence of observation for orthogenesis: an 
evidence of two categories, namely, positive affirmative 
evidence, * and negative evidence drawn from the inade- 
quacy of other theories, notably natural selection, to explain 
certain observed phenomena which can be explained on the 
assumption of an orthogenesis. The general character of 
this evidence is indicated in our first paragraph treating of 

orthogenesis. To this may be added an ab- 
aie eta stract of Plate’s’*® résumé of the facts or 
to prove ortho- phenomena which may be looked on as positive 
Seer evidence for orthogenesis (although Plate cau- 
tiously notes that some of these may be only phenomena of 
orthoselection). These phenomena pointing toward ortho- 
genesis may be grouped into six categories: 

I. The “analogous or parallel variations” which have 
been recognised ever since Darwin’s time, he, himself, list- 
ing many examples of them. These are varia- 
tions of unmistakably similar character, which 
often appear in different branches of the same 
large group. “Comparative anatomy reveals many ex- 


Pafallelisms in 
variation, 


280 DARWINISM TO-DAY. 


amples to show that a definite or determinate direction of 
modification may be noted in all the sub-groups of a large 
family, although appearing in unequal degree in different 
species. Examples are the reduction of the hind toes among 
the Artiodactyls which has continued in several genera 
(giraffe, camel, llama) up to a complete disappearance, and 
the modification of the originally single genital duct into a 
double and finally triple one, as occurs in both the Pul- 
monata and the Opisthobranchiata. Often a progressive 
development can, on mechanical or physical grounds, come 
_ about by a modification in but one direction, and may lead 
3 thus to convergent changes, as the development of a lens in 
a pigment fleck in the case of many unrelated lower animals, 
the similarity of the heart in crocodiles, birds, and mammals, 
the appearance of a placenta with Permales among the 
Marsupials and also among the Placentalia.”’ 

2. The numerous “excessive structures’ which are de- 
veloped far beyond the limits of usefulness. Examples, the 
tusks of the wild boar (Babirussa alfurus) ; the 
giant horns of many wild sheep and goats; 
the enormously elongated thread-like neck of 
several Rhynchophorous beetles, as Apoderus tenuissimus, 
etc.; the absurdly long eye-stalks of such crustaceans as 
Macrophthalmus laterillei and Podophthalmus vigil; Meso- 
plodon, whose mouth can be opened but a little when 
the animal is full grown because on each side an under 
tooth grows around the upper jaw. Such “excessive 
structures” have undoubtedly led to the dying out of many 
former species: examples, the tusks of the mammoth, the 
antlers of the Irish stag, the canines of Smilodon neogeus. 

3. “The constitution, or actual chemical composition of the 
body permits, in many cases, changes only in few directions. 
The animal or plant breeder may by no means produce any 
wished-for form or colour. No one has yet succeeded in 
producing a blue Maiblume, a grass with divided leaves, a 


Over-speciali- 
gations. 


OTHER THEORIES OF SPECIES-FORMING. 288 


hen with a parrot’s beak. And we can declare with con- 
fidence that a chorda dorsalis can never appear in a beetle. 

Gaiam Through the very fact that an animal belongs. 
limitationson to a group the possibilities of variation are 
beater distinctly delimited and in many special cases 
these possibilities may indeed be very narrow.” Plate 
does not mention in this connection the fact that some 
biologists have seen in this restriction of the range of varia- 
tion which inevitably accompanies specialisation in the ~ 
development of animal groups an important factor in- the 
determination of lines of descent. Cope gave much import- 
ance to this factor, and very recently Rosa,’* in a most in- 
genious and suggestive paper, attributes to this “progressive 
reduction of variability” a large importance in the dying 
out of old species and the origin of new ones. 

4. “By the correlations which bind each organ to others. 
the range of variation is also restricted.” 

5. Many facts of paleontology seem to prove the existence 
of orthogenetic evolution. “Wherever a large supply of ma- 

Factsfrom terial permits the working out of a phyletic 
rene series, we always see a limited number of lines 
thogenesis, of development, which despite occasional side- 
branching run essentially in straight lines, in steps which 
lead gradually one to another.” 

6. The phyletic series (chains of forms) of recent species 

Single phy- also show, where we are able to trace them, 
letic lines. distinctive single lines of development. 

Eimer’s particular theory of orthogenesis, which we 
have chosen as a representative of the orthogenetic doc- 
trine in general (although few biologists who believe in 
the principle of orthogenesis accept this theory in detail), 
may be briefly stated as follows: 

Modifications of organisms, that is, lines of evolution, are 
not miscellaneous, but occur according to control along a 
few definite directions, these lines of change being deter- 


of orthogenesis. 


282 DARWINISM TO-DAY. 


mined not at all, at least in their beginnings, by selection on 
a basis of utility, but as the result of the inheritance of ac- 
quired characters and according to the laws 
of organic growth (organophysis). The prin- 
cipal effects of these laws of organic growth are 


Eimer’s theory 


made manifest by the determinant evolution, or orthogenesis, 


which obtains, and which is in direct contrast to that kind of 
evolution which natural selection, if it really effected any- 
thing, would bring about. For evolution by natural selec- 
tion would occur along all sorts of heterogeneous and radiat- 
ing lines which is, according to Eimer, actually not the 


case. A few definite lines obtain from which occasional 


branches are given off, the whole building the familiar 


phyletic or genealogical tree. That these main lines and 


branches are not themselves the result of selection is proved 
by the fact that much evolution and modification of organ- 
isms is not directly useful, a majority, indeed, of the char- 
acters distinguishing different species not being characters 


yo! utility."" Only when a character or line of evolution 


‘becomes of a life-and-death-determining disadvantage can 
selection interfere with evolution by orthogenesis. And this 
interference is always and only of the nature of a stamping 
out, never of the character of the creation of new characters 
or lines. Eimer believes in the inheritance of acquired 
characters, believes in a considerable species-forming influ- 
ence of geographical isolation, that is, finds such isolation 
very helpful to the general basic organic growth evolution 
principle and finds the actual causes of orthogenesis “‘to 
lie in the effects of external influences, climate, nutrition, 
on the given constitution of the organism.” “This is not 
Lamarckism,” Eimer points out, anxious to have his theory 
to his own credit, “for Lamarck ascribed to the external in- 
fluences no effects on the animal body, and only very little 
on the plant body.” Eimer adds that the effects of external 
influences are usually considered a part of Lamarckism; 


OTHER THEORIES OF SPECIES-FORMING. 283 


as a matter of fact Lamarck’s species-forming influences 
were, chiefly at least, the inherited results of actual use or 
disuse, or of other functional stimulation initiated or exer- 
cised actively by the organism itself. In the actual varia- 
tion of organisms Eimer sees none of that “oscillation” or 
equal variation around a median or modal point character- 
istic of the Darwinian conception, but sees always a deter- 
minate variation in a few definite lines. He denies positively 
any capacity on the part of natural selection to create species, 
finding it effective in breaking the continuous organic chain, 
that is, of separating it into species, only when aided by 
geographical isolation. The actual species-forming, that is, 
the breaking up into specific units of the orthogenetic lines 
of change instituted by his dynamic factors, he finds to de- 
pend on three chief moments, viz., a standing still or cessa-/ . 
tion of development (Entwicklungsstillstand) ; a sudden de- 4. 
velopment by leaps, called halmatogenesis (which is almost 
exactly the fundamental idea in Korschinsky’s and de Vries’s 
later heterogenesis theory) ; and third, a hindrance or diffi- 7 
culty in reproduction (which is the essential factor in Ro- 
manes’s theory of physiological selection proposed ten years 
later). It is of interest to note Eimer’s claim to the original 
conception of species-forming both by heterogenesis and 
through physiological selection, with which two theories 
the names of de Vries and Romanes, respectively, are com- 
monly associated as those of the original proposers. 

Of Eimer’s three species-forming factors he lays most 
stress on the one I have first mentioned viz., Entwicklungs- 
stillstand. “The origin of species depends essentially on 
Enturcklungsstillstand or Genepistase, that is, the standing 
still of certain forms at definite stages in the developmental || 
line, while others go on.” This permits of the origin of 7 
numerous different species in the same locality or region, 
without any need of isolation. As orthogenesis modifies, 
that is, causes to vary in the same way, many individuals at 


nee 


rs. 


/ 
f 
| 
i 3 
| 


; 
a 
3 


= 


284 DARWINISM TO-DAY. 


a time, it is easy to see that if some of these produce young 
which do not proceed farther along the orthogenetic line, 
that is, do not vary farther, while others produce progeny 
that tend to move on along the line or lines of determinate 
variation, new species can be dropped, as it were, out of th 
general course of the orthogenetic evolution all along. An, 
if these persist we have a series of distinct organic forms all 
related chainwise although living simultaneously and in the 
same region. This cessation of development can lead to 
many added new forms when it occurs in the form of 
Heterepistase, that is, where only a few characteristics re- 
main fixed at some early developmental stage while others 
goon. By the fixing or cessation of development in differ- 
ent small groups of characteristics, and in different combina- 
tions of these groups many new species may result. All 
cases of so-called atavism are interpreted by Eimer simply 
as examples of his Entwicklungsstillstand, this cessation of 
development occurring in the atavistic organs at a very early 
stage. 

We should not omit mention, in connection with Eimer’s 
theory, of a point upon which he lays great stress, and that 
is that his theory is not the result of pure speculation, but is 
' the unavoidable conclusion arrived at by long years of 


' | specific observations and study of the facts obtaining in the 


' | case of the relations, conditions, and course of evolution of 


| certain groups of organisms. Eimer made careful and ex- 


tended studies of the wing-patterns of two large groups of 
butterflies, and of certain lizards and birds, and it is on the 
basis of these studies in particular that his theory was 
formulated. It is certainly to be admitted that his exhaust- 
ive and most suggestive account of the relations of species 
and patterns in the swallow-tailed and certain other butter- 
flies makes a very strong argument against the validity of 
natural selection as an explanation of these conditions. And 
the example of Eimer’s prolonged and minute study of. 


OTHER THEORIES OF SPECIES-FORMING. 285 


actual facts as a basis for his theory and hypothesis building 
is one which has not been always followed by biological 
generalisers. It is to be regretted that the polemical and 
personal character of much of Eimer’s writing has tended 
to make his whole work less regarded than it ought to be 
by biologists. 

That Eimer’s theory does not include in any degree the 
assumption of an inner directive or progressive force the 
following quotation from Eimer himself shows: “Accord- 
ing to my investigations the chief cause of transformation 
[of species] is that determined definitive organic growth 
(organophysis) whose expression is a definite determined 
development (orthogenesis), which is imposed on the 
plasma by constant outer influences, climate, and nourish- 
ment. . . . Apart from the fact that the Nagelian assump- 
tion of a definite determined development is a hypothetical 
one, not proved by facts, the zoologist can hardly accept the 
existence of such a dominant inner factor ever pushing 
toward advance, when he recalls the host of regressive struc- 
tures which he has to see. This tendency to progress based 
on the assumption of ‘inner growth laws’ contradicts 
flatly the assumption of outer influences as causes of 
Chanpe.)steeeena sit is) my” belief that. vit is precisely 
these outer influences, and the physiological phenomena 
dependent on them, which are the determining factors in 
the phyletic development just as they are in individual 
development.” *° 

Among American biologists who have been believers, in 
some degree, in Lamarckism or some other form of ortho- 
genetic evolution, Cope is the one who has most 
definitely formulated his beliefs into a complete 
theory of the method of creating and guiding 
variation and descent lines. Cope’s theory may be called 
one of bathmism (growth-force), kinetogenesis (direct effect 
of use and disuse and environmental influence), and arch- 


Cope’s ortho- 
genetic theory, 


286 DARWINISM TO-DAY. 


esthetism (influence of primitive consciousness). In am 
essay” first published by Cope in 1871 the following 
hypotheses were presented. (These hypotheses are stated 
here in Cope’s own words, quoted from the preface of his 
book “The Origin of the Fittest,’ 1887) : 

“tT. The law of repetitive addition, in which the structures 
of animals were shown to have originated from simple 
repetitions of identical elements. 

“2, The existence of an especial force which exhibits 
itself in the growth of organic beings, which was called 
growth-force, or bathmism. 

“3, That development consists in the location of this 
energy at certain parts of the organism. 

“a. That this location was accomplished by use or effort, 
modifying and being modified by the environment; or the 
doctrine of kinetogenesis. 

“Ss. That the location of this energy at one point causes its 
abstraction from other points, producing ‘complementary 
diminution’ of force at the latter. 

“6. That the location of this energy, so as to produce the 
progressive change called evolution, is due to an influence 
called ‘grade influence.’ 

“7. That inheritance is a transmission of this form of 
energy, which builds in precise accord with the sources 
from which it is derived. 

“8. That this ‘grade influence’ is an expression of the in- 
telligence of the animal, which adapts the possessor to the 
environment by an ‘intelligent selection.’ 

“g. An attempt to account for the origin of ‘mimetic 
analogy’ by ‘maternal impressions.’ ” 

In later writings ** Cope subdivides his kinetogenesis prin- 
ciple, or the influence of use, disuse, and environment, into 
a physico-chemical influence affecting the organism through 
molecular effects, which he calls physiogenesis, and a me- 
chanical influence affecting the organism through molar 


OTHER THEORIES OF SPECIES-FORMING. 287 


effects, for which the term kinetogenesis is retained. The 
modifications produced by these two classes of influences: 
“are supposed to be the result of the action of the causes in 
question continued throughout geologic time.” These: 
modifications are assumed to be inherited. In the animal 
kingdom kinetogenesis, or the modifying influence of mo- 
tion, is assumed to be the more potent efficient cause of 
evolution; in the plant kingdom, physiogenesis. The gen- 
eral standpoint of Cope’s theory is thus strictly Lamarckian. 
But he adds to this reformulation of general Lamarckism a 
remarkable feature which he calls archesthetism. This is: 
the doctrine that “animal movements are primitively deter- 
mined by sensibility or consciousness” and that this “con- 
sciousness has been and is one of the primary factors in the 
evolution of animal forms.” That is, the kinetogenesis. 
which is the chief causo-mechanical factor of the evolution 
of the animal kingdom, from primitive single-cell type to 
most complex Metazoan, has for its own initiation conscious 
effort. Thus Cope is forced to assume, which he does, that 
“conscious states have preceded organisms in time and 
evolution.” The formal statement of this phenomenon, 
then, has to be the thesis that energy can be conscious. “If 
true,’ writes Cope, “this is an ultimate fact, neither more 
nor less difficult to comprehend than the nature of energy 
or matter in their ultimate analyses. But how is such a 
hypothesis to be reconciled with the facts of nature, where 
consciousness plays a part so infinitesimally small? The 
explanation lies close at hand, and has been already referred 
to. Energy become automatic is no longer conscious, or is 
about to become unconscious.” Cope holds then that “con- 
sciousness was coincident with the dawn of life,” and that |, 
“evolution is essentially a process of mind. The source of | 
the consciousness, which is back of it, is at present an un-— 
solved problem.” 

Cope was a paleontologist,** and his belief in the necessity 


288 DARWINISM TO-DAY. 


of some factor or factors besides that of natural selection 
to explain evolution lines as revealed by palzontological 
study is shared by a large majority of the recognised 
American palzontologists. Osborn of Columbia, Williston 
of Chicago, Hyatt of Boston, Smith of Stanford, studying 
respectively the fossil mammals, the reptiles, and the 
molluscs, all voice their belief in the existence of evidence in 
the history of the evolution of these animal groups for 
orthogenetic variation and descent. 
Recently Whitman, the Nestor of American zoologists, 
has declared himself strongly as an adherent of the actuality 
of orthogenetic evolution. For many years 
eae Whitman has been studying the variations and 
pression in S 
aaah: ortho- inheritance in pigeons, and through this work 
| in particular he has become convinced that 
species-forming variation does advance in a definite direc- 
tion as well as in various directions. He says,” “natural 
selection, orthogenesis,” and mutation appear to present 
fundamental contradictions; but I believe that each stands 
for truth, and reconciliation is not distant. The so-called 
mutations of Cénothera are indubitable facts; but two lead- 
ing questions remain to be answered. First, are these muta- 
tions now appearing, as is agreed, independently of varia- 
tion, nevertheless a production of variations that took place 
at an earlier period in the history of these plants? Sec-: 
ondly, if species can spring into existence at a single leap, 
without the assistance of cumulative variations, may they 
not also originate with such assistance? That variation 
does issue a new species, and that natural selection is a 
factor, though not the only factor, in determining results, 
is, In my opinion, as certain as that grass grows although 
we cannot see it grow. Furthermore, I believe I have 
found indubitable evidence of species-forming variation 
advancing in a definite direction (orthogenesis), and like- 
wise of variations in various directions (amphigenesis). If 


OTHER THEORIES OF SPECIES-FORMING, | 289 


I am not mistaken in this, the reconciliation for natural 
selection and orthogenesis is at hand” (p. 4). 

In the category of determinate or orthogenetic variation 
should be included Delage’s ** not very clearly distinguished 

Detage the: variation générale. “We call by the name of 
ory ofgeneral general variation,” he says, “that which appears 
pt eet at one time in all the individuals of a race or 
at least a large number of individuals and which affects, 
most often, several characteristics, if not all, in various 
degrees of strength. Variations of this sort must be due 
to modifications of the germ plasm produced either by the 
reducing division, or by fertilisation, or by accidental altera- 
tions which this plasm undergoes in its various divisions.” 
It is to these variations, according to Delage, that species- 
change is due. The inducing influences which result in the 
appearance of general variations are use and disuse and the 
“conditions of life” (nutrition and climate). 

As forming a sort of link between the theories of ortho- 
genesis and those of heterogenesis (to be discussed in the 

Ete next chapter), may be mentioned the rather 
theory of vague and unformed theory of Jaeckel,”’ the 
metakinesis. § Berlin paleontologist, called ‘“metakinesis.” 
Jaeckel believes, from a study of fossil animal series, that 
there exists evidence of orthogenetic descent, but that while 
genera and families may show continuous phyletic series, 
species appear sporadically, suddenly, and without special 
reference to the phyletic series. He believes that many cases 
of epistasis occur: that is, that many sexually mature ani- 
mals show arrests of development in early ontogenetic 
stages, and have therefore given up a former further 
development. He finds numerous examples of this condi- 
tion among fossil crinoids and trilobites and living sela- 
chians. What his theory of metakinesis really seems to be 
is a combination of the sudden, definitive appearance of new 
species, which is the essential conception in the theories of 


290 DARWINISM TO-DAY. 


heterogenesis (explained in the next chapter), with the 
determinate lines of change or descent, which is the essential 
idea in orthogenesis. 


APPENDIX. 


* Lamarck, 1744-1828, the “founder of the complete modern theory 
of descent, is the most important figure [in the history of the 
References to theory of evolution] between Aristotle and Darwin” 
Lamarck’s (Osborn, “‘From the Greeks to Darwin,” p. 156, 1899). 
writings. His theory of descent and the causes of descent was 
presented in his ‘‘Philosophie Zoologique,” a large work published in 
1809. For a brief account of Lamarck’s life and work, see Osborn, 
“From the Greeks to Darwin,” pp. 156-181, 1899. For an exhaustive 
account with full quotations from Lamarck’s exposition of his the- 
ories, see Packard, ‘““Lamarck, His Life and Work,” 1901. For ex- 
positions of the Lamarckian point of view compared with the Dar- 
winian position, see Haeckel, E., ““Die Naturanschauung von Darwin, 
Goethe, und Lamarck,” 1882; Lang, A., “Zur Characteristik der For- 
schungswege von Lamarck und Darwin,’ 1889; Ward, L. F., “Neo- 
Darwinism and Neo-Lamarckism,” Proc. Biol. Soc., Wash., Vol. VI, 
pp. 11-71, 1891; Hutton, F. W., “Darwinism and Lamarckism, Old 
and New,” 1899; Pauly, A., “Darwinismus und Lamarckismus,” 1905. 
* Among the more conspicuous of these cases are Brown-Séquard’s 
epileptic guinea-pigs, Hyatt’s Planorbis shells, Cunningham’s flat- 
Brown-8é- ‘fishes, and Fischer’s butterflies. | Morgan, in ‘““Evo- 
quard’s experi- lution and Adaptation,” gives the following account 
ments on guinea- and discussion of the Brown-Séquard experiments 
pees and results: ““The best direct evidence in favour of the 
Lamarckian argument is that furnished by the experiments of Brown- 
Séquard. He found, as the result of injury to the nervous system of 
guinea-pigs, that epilepsy appeared in the adult animal, and that young 
born from these epileptic parents became also epileptic. Still more 
important was his discovery that, after an operation on the nerves, 
as a result of which certain organs, the ear or the leg, for instance, 
are affected, the same affection appears in the young born from 
such parents. These results of Brown-Séquard have been vouched 
for by two of his assistants, and his results in regard to the inheri- 
tance of epilepsy have been confirmed by Obersteiner, and by 
Luciani on dogs. Equally important is their later confirmation, as 
far as the main facts go, by Romanes. 
“Brown-Séquard gives the following summary of his results. 
I follow Romanes’ translation in his book on ‘Darwin and After 


OTHER THEORIES OF SPECIES-FORMING. 29g! 


Darwin, where there is also given a careful analysis of Brown- 
Séquard’s results, as well as the outcome of the experiments of 
Romanes himself. The summary is as follows :— 

“Tt, ‘Appearance of epilepsy in animals born of parents which had 
been rendered epileptic by an injury to the spinal-cord. 

“2. ‘Appearance of epilepsy also in animals born of parents 
which had been rendered epileptic by section of the sciatic nerve. 

“3. ‘A change in the shape of the ear in animals born of parents 
in which such a change was the effect of a division of the cervical 
sympathetic nerve. 

“4. ‘Partial closure of the eyelids in animals born of parents in 
which that state of the eyelids had been caused either by section 
of the cervical sympathetic nerve, or the removal of the superior 
cervical ganglion. 

“5. ‘Exophthalmia in animals born of parents in which an injury 
to the restiform body had produced that protrusion of the eyeball. 
This interesting fact I have witnessed a good many times, and seen 
the transmission of the morbid state of the eye continue through 
four generations. In these animals modified by heredity, the two 
eyes generally protruded, although of the parents usually only one 
showed exophthalmia, the lesion having been made in most cases 
only on one of the corpora restiformia. 

“6. ‘Hematoma and dry gangrene of the ears in animals born 
of parents in which these ear alterations had been caused by an 
injury to the restiform body near the nib of the calamus. 

‘7 “Absence of two toes out of the three of the hind-leg, and 
sometimes of the three, in animals whose parents had eaten up 
their hind-leg toes, which had become anesthetic from a section 
of the sciatic nerve alone, or of that nerve and also of the crural. 
Sometimes, instead of complete absence of the toes, only a part 
of one or two or three was missing in the young, although in 
the parent not only the toes, but the whole foot was absent » 
(partly eaten off, partly destroyed by inflammation, ulceration, or 
gangrene). 

“8. ‘Appearance of various morbid states of the skin and hair 
of the neck and face in animals born of parents having had similar 
alterations in the same parts as effects of an injury to the sciatic 
nerve.’ 

“Romanes, who later went over the same ground, in part under 
the immediate direction of Brown-Séquard himself, has made some 
important observations in regard to these results, many of which 
he was able to confirm. 

“He did not repeat the experiment of cutting the cord, but he 
found that, to produce epilepsy, it was only necessary to cut the 


292 DARWINISM TO-DAY. 


sciatic nerve. The ‘epileptiform habit’ does not appear in the animal 
until some time after the operation; it lasts for some weeks or 
months, and then disappears. The attacks are not brought on spon- 
taneously, but by ‘irritating a small area of the skin behind the 
ear on the same side of the body as that on which the sciatic nerve 
had been divided.’ The attack lasts for only a few minutes, and 
during it the animal is convulsed and unconscious. Romanes thinks 
that the injury to the sciatic nerve, or to the spinal cord, produces 
some sort of a change in the cerebral centres, ‘and that it is this 
change—whatever it is, and in whatever part of the brain it takes 
place—which causes the remarkable phenomena in question.’ 

“In regard to Brown-Séquard’s statements, made in the 3d and 
the 4th paragraphs, in respect to the results of the operation of - 
cutting the cervical sympathetic, Romanes had not confirmed the 
results when his manuscript went to press; but soon afterward, 
after Romanes’ death, a note was printed in Nature, by Dr. Hill, 
announcing that two guinea-pigs from Romanes’ experiment had 
been born, ‘both of which exhibited a well-marked droop of the 
upper eyelid. These guinea-pigs were the offspring of a male and 
female in both of which I had produced for Dr. Romanes, some 
months earlier, a droop of the left upper eyelid by division of the left 
cervical sympathetic nerve. This result is a corroboration of the 
series of Brown-Séquard experiments on the inheritance of acquired 
characters.’ 

“Romanes states that he also found that injury to a particular 
spot of the restiform bodies is quickly followed by a protrusion 
of the eye on the same side, and further, that he had ‘also had 
many cases in which some of the progeny of parents thus affected 
have shown considerable protrusion of the eyeballs of both sides, 
and this seemingly abnormal protrusion has occasionally been 
transmitted to the next generation. Nevertheless, I am far from 
satisfied that this latter fact is anything more than an accidental 
coincidence. This reservation is made on the ground that the 
protrusion in the young is never so great as in the parents, and 
also because there is amongst guinea-pigs a considerable amount 
of individual variation in the degree of prominence of the eye- 
balls. Romanes, while unwilling to deny that an ‘obviously abnor- 
mal amount of protrusion, due to the operation, may be inherited 
in lesser degree,’ is also unwilling to affirm so important a conclu- 
sion on the basis of these experiments alone. 

“In regard to Brown-Séquard’s 6th statement, Romanes found 
after injury to the restiform body that hematoma and dry gan- 
grene may supervene, either several weeks after the operation, or 
at any subsequent time, even many months afterward. The disease 


OTHER THEORIES OF SPECIES-FORMING. 293 


usually affects the upper parts of both ears, and may then gradually 
extend downward until nearly the whole ear is involved. ‘As re- 
gards the progeny of animals thus affected in some cases, but by 
no means in all, a similarly morbid state of the ears may arise 
apparently at any time in the life history of the individual. But 
I have observed that in cases where two or more individuals of the 
same litter develop this diseased condition, they usually do so at 
about the same time, even though this may be months after birth, 
and therefore after the animals are fully grown.’ Moreover, the 
morbid process never extends so far in the young as it does in the 
parents, and ‘it almost always affects the middle third of the ear.’ 
Several of the progeny from this first generation, which had appa- 
rently inherited the disease, but had not themselves been directly 
operated upon, showed a portion of the ear consumed apparently 
by the same disease. Romanes then gives the following signifi- 
cant analysis of this result. Since a different part of the ear 
of the progeny is affected, and also a ‘very much less quantity 
thereof, it might seem that the result was due either to a mere 
coincidence, or to the transmission of microbes. But he goes on 
to say, that he fairly well excluded both of these possibilities, for, 
in the first place, he has never observed ‘the very peculiar process 
in the ears, or in any other parts of guinea-pigs which have neither 
themselves had the restiform bodies injured, nor been born of 
parents thus mutilated.’ In regard to microbes, Romanes tried to 
infect the ears of normal guinea-pigs by first scarifying these parts, 
and then rubbing them with the diseased surfaces of the ears of 
affected guinea-pigs. In not a single case was the disease produced. 

“Romanes concludes that these ‘results in large measure corrobo- 
rate the statements of Brown-Séquard; and it is only fair to add 
that he told me they were the results which he had himself obtained 
most frequently, but that he had also met with many cases where the 
diseased condition of the ears in parents affected the same parts in 
their progeny and also occurred in more equal degrees.’ 

“We come now to the remarkable conclusion given in Brown- 
Séquard’s 7th statement, in regard to the absence of toes in animals 
whose parents had eaten off their own hind toes and even parts 
of their legs. Romanes got neuroses in the animals operated upon, 
and found that the toes might be eaten off; but none of the young 
showed any defect in these parts. Furthermore, Romanes repeated 
the same operation upon the descendants through six successive 
generations, so as to produce, if possible, a cumulative effect, but no 
inheritance of the mutilation was observed. ‘On the other hand, 
Brown-Séquard informed me that he had observed this inherited 
absence of toes only in about one or two per cent. of cases.’ It is 


294 DARWINISM TO-DAY. 


possible, therefore, Romanes adds, that his own experiments were 
not sufficiently numerous to have obtained such cases. 

“In this connection I may give an account of some observa- 
tions that I made while carrying out some experiments in telegony 
with mice. I found in one litter of mice that when the young came 
out of the nest they were tailless. The same thing happened again 
when the second litter was produced, but this time I made my 
observation sooner, and examined the young mice immediately after 
birth. I found that the mother had bitten off, and presumably 
eaten, the tails of her offspring at the time of birth. Had I been 
carrying on a series of experiments to see if, when the tails of the 
parents were cut off, the young inherit the defect, I might have 
been led into the error of supposing that I had found such a case in 
these mice. If this idiosyncrasy of the mother had reappeared in 
any of her descendants, the tails might have disappeared in suc- 
ceeding generations. This perversion of the maternal instincts is 
not difficult to understand, when we recall that the female mouse 
bites off the navel-string of each of her young as they are born, 
and at the same time eats the afterbirth. Her instinct was carried 
further in this case, and the projecting tail was also removed. 

“Is it not possible that something of this sort took place in 
Brown-Séquard’s experiment? The fact that the adults had eaten 
off their own feet might be brought forward to indicate the possi- 
bility of a perverted instinct in this case also. At least my obser- 
vation shows a possible source of error that must be guarded 
against in future work on this subject. 

“In regard to the 8th statement of Brown-Séquard, as to various 
morbid states of the skin, Romanes did not test this, because the 
facts which it alleges did not seem of a sufficiently definite character. 

“These experiments of Brown-Séquard, and of those who have 
repeated them, may appear to give a brilliant experimental confirma- 
tion of the Lamarckian position; yet I think, if I were a Lamarckian, 
I should feel very uncomfortable to have the best evidence in sup- 
port of the theory come from this source, because there are a 
number of facts in the results that make them appear as though 
they might, after all, be the outcome of a transmitted disease, as 
Weismann claims, rather than the inheritance of an acquired char- 
acter. Until we know more of the pathology of epilepsy, it may 
be well not to lay too great emphasis on these experiments. It 
should not be overlooked that during the long time that the embryo 
is nourished in the uterus of the mother, there is ample opportu- 
nity given for the transmission of material, or possibly even of 
bacteria. If it should prove true that epilepsy is due to some sub- 
stance present in the nervous system, such substances could get 


OTHER THEORIES OF SPECIES-FORMING. 295 


there during the uterine life of the embryo. Even if this were the 
case, it may be claimed that it does not give an explanation of the 
local reappearance of the disease in the offspring. But here, also, 
we must be on our guard, for it is possible that only certain regions 
of the body are susceptible to a given disease; and it has by no 
means been shown that the local defect itself is inherited, but only 
the disease. Romanes insists that a very special operation is neces- 
sary to bring about certain forms of transmission.” 

The case of the Planorbis shells studied by Hyatt (Proc. Amer. 
Phil. Soc., Vol. XXXII, p. 615 ff.) has been interestingly dis- 

Hyatt’s studies cussed by Le Dantec (“Traité de Biologie,” pp. 296 
of Planorbis. ff., 1903) as follows: “On trouve, dans les terrains 
trés anciens, des coquilles de Céphalopodes qui ont la forme d’une 
corne de vache et dont la section transversale est a peu pres circu- 
laire; en suivant la série des fossiles de cette catégorie dans 
des terrains plus récents, on constate que ces coquilles, presque 
droites naguére, se sont enroulées de plus en plus a la maniére 
d’une spirale d’Archiméde; nous ne connaissons pas la raison 
de cette transformation, mais la présence de certains caractéres 
communs permet de considérer comme démontré que les formes 
enroulées descendent des animaux a coquilles droites. Or, l’enroule- 
ment est tellement fort dans certains types que les tours de 
spire successifs simpriment les uns dans les autres, donnant nais- 
sance a un sillon dorsal dont la genése mécanique est évidente, 
puisqu’il résulte sans conteste de la pression du tour de spire 
précédent sur le suivant. 

“Tant que les animaux en question restent aussi nettement 
enroulés, on peut admettre que ce caractére de l’existence d’un sillon 
dorsal est acquis individuellement par chaque Céphalopode pour des 
raisons mécaniques évidentes, le contact des tours de spires. 

“Mais voila qu’a une période plus récente de l’histoire du monde, 
les découvertes paléontologiques nous montrent que les descendants 
de ces Céphalopodes a coquille enroulée ont subi un commencement 
de déroulement et ont maintenant la forme d’une spirale’ d’Archi- 
meéde a tours de spires plus écartés les uns des autres et ne se 
touchant plus; et notez bien que des caractéres communs permettent 
d’affrmer que ces Céphalopodes a moitié déroulés descendent de 
ceux dont l’enroulement était beaucoup plus serré. 

“Or, chose admirable, le sillon dorsal persiste chez ces étres a 
coque a moitié déroulée! Cependant il n’y a plus maintenant 
pression d’un tour de spire sur le tour de spire précédent; nous 
avons compris mécaniquement la genése de ce sillon dorsal, quand 
les tours de spire se touchaient et se pressaient l’un l’autre; et ce 
sillon persiste en dehors des conditions mécaniques ot il a été 


296 DARWINISM TO-DAY. 


d’abord produit; il se transmet a des descendants dont la coquille 
est déroulée! C’est done que le patrimoine héréditaire a été 
modifié sous Vinfluence de la production mécanique de ce sillon 
dorsal, au point de devenir adéquat a cette forme nouvelle d’équi- 
libre; il y a un nouveau patrimoine héréditaire, qui construisant un 
individu nouveau et son squelette, fera apparaitre, sans pression, 
le sillon dorsal!” 

The results of the experiments of Cunningham on flatfishes are 
stated by the author, in a paper on “The Problem of Variation,” 
Nat. Sci., Vol. III, p. 285, 1893. Cunningham put the very young 
fish, while still bilaterally symmetrical (in which stage the pigment 
is equally developed on both sides of the body), into aquaria lighted 
from below. He found that when the young fish begins to undergo 
its metamorphosis, the pigment gradually disappears on one side, 
as it would have done under normal conditions, 7. e., when they are 
lighted from above. If, however, the fish are kept for a short time 
longer, lighted from below, the pigment begins to come back again. 
“The first fact,” says Cunningham, ‘‘proves that the disappearance 
of the pigment-cells from the lower side in the metamorphosis is a 
hereditary character, and not a change produced in each individual 
by the withdrawal of the lower side from the action of the light. 
On the other hand, the experiments show that the absence of pig- 
ment-cells from the lower side throughout life is due to the fact that 
light does not act upon that side, for, when it is allowed to act, 
pigment-cells appear. It seems to me that the only reasonable con- 
clusion from these facts is that the disappearance of the pigment- 
cells was originally due to the absence of light, and that the change 
has now become hereditary. The pigment-cells produced by the 
action of light on the lower side are in all respects similar to 
those normally present on the upper side of the fish. If the dis- 
appearance of the pigment-cells was due entirely to the variation 
of the germ-plasm, no external influences could cause them to re- 
appear; and if there were no hereditary tendency, the coloration 
of the lower side of the flatfish would be rapid and complete.” 

Concerning Fischer’s highly interesting experimental work, I 
quote the following paragraph from Fuchs, H. (Biol. Centralbl., 

Fischer's ex- Wol. XXI, pp. 591-592, 1901; Fischer’s own papers 
periments with have been published in various biological journals, 
butterflies: the particular one recounting the results obtained 
with Arctia caja in the Allg. Zeitschr. fiir Entomologie, Vol. 
Visioo2 ye 

“Experimentelle Untersuchungen, ob es moglich sei, durch will- 
kurliche, geeignet gewahlte Veranderungen der “ausseren Lebens- 
bedingungen, besonders der Temperaturverhaltnisse, im Tierreiche 


OTHER THEORIES OF SPECIES-FORMING. 207 


Variationen bei den Arten hervorzurufen, wurden in den letzten 
Decennien wiederholt angestellt; mit Vorliebe hat man sich dabei 
als Versuchsobjekte die Schmetterlinge gewahlt: ich erinnere z. 
B. an die schonen Versuche von Standfuss und E. Fischer. Das 
Resultat war—wie ja nach unseren heutigen Anschauungen wtber 
den ziichtenden Einfluss der Faktoren der Aussenwelt auf alle 
Organismen eigentlich kaum anders zu erwarten stand—positiv. 
Eine Frage allerdings, an welche bei diesen Untersuchungen wohl 
jeder der Forscher dachte, namlich: ob die auf solche Weise 
erworbenen Eigenschaften und Abanderungen auch auf die eventu- 
ellen Nachkommen tibertragen, also vererbt wurden oder doch 
wenigstens werden konnten, blieb dabei einstweilen unentschieden. 
Erst kiirzlich gelang es E. Fischer, auch ftir dieses Postulat der 
modernen Biologie einen vollgiltigen Beweis beizubringen. F. expe- 
rimentierte mit Arctia caja, dem braunen Bar, der ja auch den 
meisten Laien—meist wohl unter dem Namen ‘deutscher Bar’— 
bekannt sein durfte, ein erfahrungsgemass fur kinstliche Varia- 
tionsversuche besonders geeignetes Tier. Durch willktrlich ge- 
wahlte Temperaturveranderungen, und zwar durch intermittierende 
Abktthlungen bis auf—8° C., denen die Puppen wiederholt ausge-- 
setzt wurden, erzielte F. stark aberrative Falter, und zwar aberrativ 
nicht nur béztiglich der ‘Farbe und Zeichnung’—wenn auch hier in 
erster Linie—sondern auch beziiglich der Form, z. B. der Flugel 
und der Beine. Dabei hebt F. ausdrticklich hervor, dass in letzterer 
Hinsicht es sich nicht etwa um Verkruppelungen handelte, sondern 
‘die Fiisse waren kraftig und mit gut ausgebildeten Krallen 
versehen. Unter diesen Varietaten gelangen nun mehrfache 
Kreuzungen; die Puppen dieser Zucht wurden unter normalen 
Bedingungen erhalten. Und siehe! von den alsbald ausgeschlupften. 
Tieren zeigte eine nicht unerhebliche Anzahl die Variationen der 
Eltern, und zwar im allgemeinen als Kombinationen aus den 
veranderten Eigenschaften beider Eltern, so dass einige mehr dem 
elterlichen Mannchen glichen, andere mehr dem elterlichen Weib- 
chen. Es ist dieses also, wie F. sagt, ein experimenteller Beweis, 
dass: 

“J. die Art durch die Faktoren der Aussenwelt Veranderungen 
erfahrt, und dass 

“2. diese Veranderungen sich auf die Nachkommen ibertragen. 

“Die Thatsache der Vererbung erworbener Eigenschaften steht 
mithin fest, wenn wir auch tiber das Wesen der ratselhaften dabei 
stattfindenden Vorgange, auf Grund dieser Untersuchungen, natiir- 
lich absolut noch nichts sagen konnen.” 

To the above cases of the alleged inheritance of acquired charac- 
ters I may add some account of certain experiments with the mul- 


298 DARWINISM TO-DAY. 


berry silkworm carried on by R. G. Bell and myself. (For detailed ac- 
count of this work see Science, N. S., Vol. XVIII, pp. 741-748, 1903.) 

“One of the races of the mulberry silkworm, Bombyx mort, has 
been the subject of experiments directed toward a determination of 
the exact quantitative relation which quantity and quality of food 
bear to the development and variations of the individual insect and 
its progeny... . 

“The insect, Bombyx mori, has a complete metamorphosis, tak- 
ing no food as an adult, so that the experimental control of the 

Experiments feeding has been necessary only during the larval or 
with silkworms. ‘silkworm’ stage. The larval life is subdivided into 
five stages clearly set off from one another by the intervening 
moults, of which there are normally four, and these substages have 
been useful when an alteration of food conditions during a sharply de- 
fined shorter time than the entire larval life was desirable... . The 
change in quantity of food has consisted in altering the amount of 
mulberry leaf served to the larve, the control of which has been 
secured as follows: It has been determined through experience with 
normal larve that each will consume a certain amount of food in 
a certain number of hours (increasing in amount with the increas- 
ing age and size of the larva), this amount representing the 
optimum amount of food for the normal individual and necessitating 
as many daily meals as are required to keep any but the moulting 
larva constantly supplied with fresh food. This amount determined, 
a tolerably definite small proportion of the optimum amount has 
been allotted the individuals which were sentenced to short rations, 
which, roughly speaking, might be listed as one-quarter the optimum 
amount during earlier stages and one-eighth during the late larval 
stages. This one-fourth, one-eighth, or whatever it may have been 
numerically, was, at any rate, as small an amount of food as was 
compatible with mere life. . 

“These experiments have extended over a period of three years, 
covering as many generations of the insect. The data gathered 
(being the measurements, weight, and duration of each larva in each 
of its five states; the time of spinning, weight of silk and. weight 
and duration of each pupa; and the weight, size, pattern, and 
fertility of female of each imago) furnish material, then, for a 
study of the effects of under-feeding upon individuals during a 
single generation (the I903 generation or that of I902 or IgoT), 
during two successive generations (IQ0I-02 or 1902-03), and two 
alternating generations (1901-1903) and during three generations 
(1901-03), a control lot having been carried for each experimental 
lot so that what is modified may confidently be distinguished from 
what is normial.... 


OTHER THEORIES OF SPECIES-FORMING. 299 


“In these variously-fed worms there exists a very definite and 
constant relation between amount of food and size as indicated by 
weight, the starveling individuals being consistently smaller than 
the well-nourished, the lingering effects of this dwarfing being 
handed down even unto the third generation, although the progeny 
of the famine generation be fed the optimum amount of food; in 
case the diminished nourishment is imposed upon three, or even 
two successive generations, there is produced a diminutive, but 
still fertile, race of Lilliputian silkworms, whose moths, as regards 
wing expanse, might join the ranks of the micro-Lepidoptera 
almost unremarked. 

“Tn illustration may be quoted the typical or modal larval weights 
for each of the lots of 1903 at the time of readiness to spin, which 
marks the completion of the feeding and is, therefore, an advan- 
tageous point for a summary of the results of the three years’ 
experimental feeding. 

“The history of the eight lots referred to may be gathered from 
an examination of the accompanying table, in which ‘O’ means 
optimum amount of food and ‘S’ means short rations. The column 
to the right indicates the relative rank of the various lots as judged 
by the modes of frequency polygons erected to include all the 
individual weights for each lot at spinning time. 


HISTORY OF LOTS. 


Toe Namber Modal Rank. 
Igor. 1902. £903¢ 
Grandparents.|Grandparents. 7903: 
Deters she ee O O O I 
fe pie Se a O O S 6 
CV tenet Aaa ae mee O S O 3 
eee sta ewe alee Oo Ss Ss 7 
huh 2 ee Ate S O O 2 
OREN eats ates 5 Ss O Ss 5 
Tie Mrerolaya, Wa Se 6! ante S Ss O 4 
See aA Sy eia'e es Ss Ss Ss 8 


“We find that control lot 1, consisting of normally-fed indi- 
viduals of normal ancestry, holds first rank in weight, as was to be 
expected. Second comes lot 5, whose grandparents experienced a 
famine but whose parents as well as themselves enjoyed years of 
plenty. Lots 2 and 3 have likewise had one ancestral generation on 
short rations, and the fact that they are lighter in weight than lot 


300 DARWINISM TO-DAY. 


5 illustrates a general rule which obtains throughout the entire 
company of experimental worms, namely, that the effects of famine 
grow less evident the further removed the individuals are from its 
occurrence in their ancestral history. Thus lot 5 is two generations 
removed from the famine of 1901, while lot 3 has had but one 
generation in which to recover its ancestral loss. Lot 2, which 
has had a total of but one famine year—the current year—neverthe- 
less ranks below lot 7, which has had two famine years in its 
ancestry succeeded by plenty during the current year. Lot 2 also 
ranks below lot 6, a fact which appears strange, considering that 
lot 6 has suffered two generations of famine, including the current 
year, which is the only famine year experienced by lot 2. In 
explanation of this anomalous condition it is suggested that possibly 
the larve of lot 6 were better fitted for enduring and making the 
best of hard conditions than were the individuals of lot 2, the 
ancestors of the former lot having been selected two years ago 
on a food-scarcity basis. This suggestion gathers support from an 
inspection of the mortality notes, from which it appears that the 
number of deaths—for which the famine was probably a contributing 
and not a primary cause—in each lot which is for the first time 
subjected to short rations is almost doubly greater than the num- 
ber of deaths in lots which are descended from starved ancestors, 
whether these ancestral famines occurred in successive or alternate 
years. The figures indicate that a reduction of food is almost twice 
as destructive upon the first generation which is subjected to it as 
it is when visited on a second generation. Lot 4 follows lot 2 as. 
the seventh in rank and its position is in accord with the rule above 
noted, its latest ancestral generation which enjoyed an optimum 
amount of food during I902 or 1903. Lot 8 holds lowest rank, 
it and its ancestors having been subject to trying conditions through- 
out the entire three years, during some one or two of which all 
the other lots have enjoyed the best of food conditions. Thus it 
appears that a generation of famine leaves its impression upon at 
least the three generations which succeed it, yet the power of 
recovery through generous feeding exhibited by the progeny of 
individuals subjected to famine, is so extensive (witness lot 5) 
that it appears probable that every trace left by the famine upon 
the race would eventually disappear. It is even conceivable that the 
ultimate result of the famine would be a strengthening of the race, 
the famine having acted the part of a selective agent, preserving 
only the strong. 

“But although there is a large difference between the well fed. 
and the poorly fed, there persists, more obviously in late than in 
early life, a very considerable discrepancy as to size among the 


OTHER THEORIES OF SPECIES-FORMING. 301 


individuals of each single lot whose environment, in so far as food, 
temperature, room, humidity, etc., constitute it, is identical. 

“For example, referring again to the weights at spinning time of 
the larve of 1903, it is true that, although each lot has a modal 
class of weights to which the majority of its individuals belong and 
about which the rest of the lot distributes itself rather symmetrically, 
the extremes are surprisingly distant from one another. Thus in 
lot 1 (the normal control lot) the, extremes are 1,540 and 2,530 
mg.; in lot 2,* 800 and 1,402 mg.; in lot 3, 1,180 and 2,170 mg.; 
in lot 4, 690 and 1,204 mg.; in lot 5, 1,370 and 2,100 mg. 

“That is to say, identical feeding has not made identical full- 
grown larve out of individuals which undoubtedly varied congeni- 
tally at the start, those variations—in embryo—standing at birth in 
the same relation to one another that they stand in the adults, hav- 
ing merely been smaller and less readily discernible in early life, 
although manifestly present in delicately measurable degree in the 
earliest records made upon normal individuals. For example, 
weight measurements taken immediately after the second moult, 
range in one lot from 21 to 39 mg., or 60 per cent. of the modal 
‘weight, while the weights in this same lot at spinning time, some 
five weeks later, range from 534 to 2,080 mg., or 85 per cent. of 
the mode for the lot. These embryonic but potentially large varia- 
tions have simply ‘grown up’ along with the insect and are as truly 
congenital in the adult as they were in the newly hatched larva. 
This would seem to place quite conclusively in the category of 
congenital variations some part of those variations (in size and pro- 
portions of parts) which are commonly, and properly to some 
degree, called acquired. 

“That conditions of alimentation bear a directive relation to func- 
tional activity, may be demonstrated by reference to the records of 
the physiological functions of moulting, spinning, pupating, and 
emerging, of the individuals of the experimental lots. 

“An abnormal extension of the time needed for the metamor- 
phosis follows upon a reduction of the food supply. The degree 
of extension depends with the utmost nicety upon the amount of 
food given the larve. For example, among the I9o0I generation of 
silkworms, one control lot of twenty larve was given the optimum 
amount of food, a second fot of twenty larve one-half this amount, 
and a third lot of twenty larve one-quarter of the amount. To 
take the time of the fourth moulting as an illustration, the moulting 
was begun by the first lot, which led the way by two and a half 
days, at the end of which the second lot began to moult, while 


* See table, next page, for the history of each lot. 


302 DARWINISM TO-DAY. 


the third lot was twenty-four hours behind the second. All the 
individuals of the first lot had finished moulting on April 20, all 
of the second on April 24, while the moulting in the third lot con- 
tinued until April 29. 

“As in the matter of weight, this retarding of the functions, by 
means of a reduced food supply, affects not only the immediate 
generation which is subjected to the famine, but the lingering effects. 
of it may be traced in the progeny of the dwarfed individuals at 
least unto the third generation, even though two years of plenty 
follow the one year of famine. The conditions which obtain in 
each lot of individuals of the 1903 generation at spinning time are 
shown in the accompanying table, which is based upon polygons 
erected to include all the individuals in each lot. 


RANK OF 1903 LOTS AS TO PROMPTNESS 
IN SPINNING. 


HISTORY OF LOTS. 


Lot When Two-thirds of Each Lot 
Num- were Spinning. 
De ; 
Earliest 
abe: Spinner. Pees reves 
es oot T902. NeOreerr ates 
aera Parents.| 19°3: Date. | of Rank. Spinner. 
i: O O O I May 12 I I 
Di. O O Ss 5 ey 4 4 
ae O S O 2 aed a 2 3 
Ae O Ss Ss 4 ZO 5 5 
cre S O O 3 hi ane be) 2 2 
Ore S O S 6 Se 2G 6 7 
ak S S O 6 ar 2o 3 5 
aa S) S S " Ate 80 | 6 


“This period in the life of the silkworms is particularly advan- 
tageous for consideration here, because it marks the completion 
of the feeding, so that the individuals of under-fed ancestry have 
been given the best chance to recover, while those subject to altered 
food conditions, had had the benefit of the alteration during the 
entire food-taking period of life. 

“In the table, ‘O’ means optimum amount of food, and ‘S’ means 
short rations. To the right of the history of the lots is a section 
showing the rank of the lots as to the extreme time limits of the 
spinning time (emphasised congenital differences again), with a 
safer criterion, as to their relative promptness, in the column be- 
tween the extremes—a column of figures intended to show the rela- 
tive promptness with which a two-thirds majority of the larve 


OTHER THEORIES OF SPECIES-FORMING., 393. 


in each lot arrives at the spinning time, this proportion being taken 
to represent the typical condition for the lot. The order in which 
the lots are arranged in this column corresponds in a general way 
with that prevalent for the weights at spinning time, and the 
generalisations indulged in there may, with few exceptions, be 
applied here. The lots which were well fed during the 1903 
generation are ahead of all of those given short rations in 1903, 
whatever ancestry they may have had. Lot 1 leads here as in the 
matter of weight. Lots 3 and 5 tie for second place, having held 
second and third places in weight. Lots 2 and 4 stand in the 
same relation to one another that they held as to weight. Con- 
trary to the weight relation, lot 6 follows lot 2 at the spinning—a 
fact which illustrates again the general rule that two generations 
of famine are more disastrous than one, but does not lend support 
to the notion of natural selection on a food scarcity basis as pre- 
viously suggested. Lot 8, which has had no relief from famine 
during the entire three years, brings up the rear at the spinning, 
as might be expected. 

“This check upon functional activity exercised by diminished nour- 
ishment affects the moulting, the time for the commencement of 
spinning, and the issuing time for the adults, but the time spent 
in the spinning of the cocoon, from its beginnings in the threads 
of the supporting net to its apparent completion when the cocoon 
becomes opaque, is practically identical for under-fed and well- 
fed individuals. A reason for this exception to the tardy habits. 
of the under-fed is to be found in the fact that the under-fed 
larve produce less silk (less in size, thickness, and weight) than the 
well-fed, thus accomplishing more meager results in the same 
amount of time. That the individuals sentenced to short rations. 
should produce less silk than their well-fed neighbours is certainly 
to be expected, silk not being made without leaves any more 
readily than bricks without straw. | 

“Not only do short rations protract the time appointed for the 
spinning, moulting, etc., but they appear to have a more striking 
effect upon the actual occurrence of the moulting. The normal 
number of moults for the silkworm larva is four. Five moults: 
have occurred for most of the individuals belonging to the under- 
fed lots of 1902 and 1903, whereas none of the well-fed individuals 
has undergone a fifth moult. It would seem, therefore, that the 
occurrence of a fifth moult may be fairly ascribed to a reduction of 
food; at least a fifth moult very frequently accompanies it and has. 
suggested the possibility that the enforced fasting of the under- 
fed larva—in the intervals between meals—may have the same 
physiological effect as the normal fasting which precedes the normal 


304 DARWINISM TO-DAY. 


moulting, during which time the so-called ‘moulting fluid’ is 
secreted. That this effect may accumulate throughout the life- 
time of the larva until the larva is actually forced to indulge in the 
extravagance (of strength, feeding time, and body wall material) 
of an additional moult is conceivable and will justify a further 
test. 

“As to the life-and-death selection due to famine, it may be 
said, in addition to the previous discussion of mortality among 
the experimental silkworms, that while lots subjected to two years 
of famine (themselves in one year, their parents in the year before) 
were fertile in so far as number of young hatched is concerned, it 
was found to be exceedingly difficult to rear from them a 1903 
generation. Indeed, at the time of the second moulting there were 
but nineteen individuals (and tolerably vigorous larve they were) 
alive in the lot which had experienced two years of famine, al- 
though every individual of the 149 hatched was carefully preserved 
and royally fed—a fact which goes to prove that the equipment at 
birth of many of these larve was inadequate. 

“The fact that some larve of starved ancestry have exhibited a 
superiority over their fellows, in surviving and recovering from 
hard conditions, is testimony for the existence of individual varia- 
tions which cannot be defined anatomically, and yet which serve as 
‘handles’ for natural selective agents. Such variations might be 
called physiological variations, since it seems that the surviving 
larve must be those which are in best trim physiologically. These 
larve are able to make the most of the food offered to them. If 
competition were allowed, they would probably be the individuals 
which would cover the area most rapidly, securing whatever food 
there might be. But under our experimental conditions there was 
no competition allowed and yet certain precocious individuals made 
more grams of flesh and more yards of silk, than other larve 
fyrnished with the same amount of raw material under like con- 
ditions; that this was due to the possession by the former of certain 
congenital qualities of adaptability can scarcely be doubted. 

“As to the fertility of the variously fed lots, in so far as number 
of eggs produced is a measure of fertility, our records already 
demonstrate the fact that the better nourished are the more fertile. 
Furthermore, the economy in this matter practised by the starve- 
lings is not merely numerical, quality as well as quantity of eggs 
being affected. In witness of this point may be recalled the story 
of the dying 1903 generation, produced from eggs of the starvelings 
of 1901 and 1902, which would seem to offer conclusive evidence 
that a famine suffered by the parents works its way into the germ- 
cells so that most of their progeny have but a poor birthright.” 


OTHER THEORIES OF SPECIES-FORMING. 395 


For special discussions of the inheritance of acquired characters, 
see the following: Roth, E., “Die Thatsachen der Vererbung,” 1885 ; 
Ziegler, E., “Konnen erworbene pathologische Eigenschaften ver- 
erbt werden und wie entstehen erbliche Krankheiten und Missbil- 
dungen,” 1886; Rohde, F., “Uber den gegenwirtigen Stand der 
Frage nach der Entstehung und Vererbung individuellen Eigen- 
schaften und Krankheiten,” 1896; Osborn, H. F., “Are Acquired 
Variations Inherited,’ 1890; Elliott, D. G., ‘The Inheritance of 
Acquired Characters,” Auk, Vol. IX, pp. 77-104, 1892; Packard, A. 
S., “On the Inheritance of Acquired Characters in Animals with 
Complete Metamorphosis,’ Proc. Amer. Acad. Science, pp. 331- 
370, 1894; Ritter, W. E., “On the Nature of Heredity and 
Acquired Characters, and the Question of the Transmissibility of 
these Characters,’ 1900; Wettstein, R. von, “Der Neo-Lamarckis- 
mus und seine Beziehungen zum Darwinismus,” 1903; Detto, Carl, 
“Theorie der direkten Anpassung,’ 1904 (good bibliography of 
papers on plant adaptations); Lendenfeld, R. V., “Variation and 
Selection,” Biol. Centralbl., Vol. XXIII, p. 489 ff., and p. 563 ff., 
1903; Pauly A., “Darwinismus und Lamarckismus,” 1905; Lotsy, 
J. P., “Vorlesungen iiber Descendenztheorien,” Vol. I, chap. xii, 
1906; Wheeler, W. M., “The Polymorphism of Ants,” Bull. of 
Amer. Mus. Nat. Hist., Vol. XXIII, pp. 1-93, Plate I-VI, January, 
1907 (see especially pp. 50-90). Certain writers of sociologic and 
philosophic interests, have discussed especially the possibility of the 
inheritance of acquired mental capacities or qualities in man; ex- 
pressing a belief in such inheritance are Biichner, “Die Macht der 
Vererbung und ihr Einfluss auf der moralischen und geistigen 
Fortschritt der Menschheit,” 1882, and Hartmann, E. V., ‘“Philo- 
sophie des Unbewussten,” toth ed.; against such an inheritance is 
Rawitz, B., “Urgeschichte, Geschichte, und Politik,’ 1903. Most 
important of all the discussions of the inheritance of acquired char- 
acters are those of Weismann, Spencer, and Eimer. 

A recent American champion of Lamarckism is Caspar |i Red: 
field, in whose writings (“Control of Heredity,’ 1903, “Evolution 

Redfield’s of the Setter,” in American Field, 1904 and 1905, and 
position. “Breeding of the Trotter,” in The Horseman, 1905) 
is urged the doctrine that acquired mental and dynamic qualities are 
inherited. On a host of data, derived from the pedigrees and 
records of trotting horses and setter dogs, Redfield keenly works out 
his inductions regarding the inheritance by young of the special 
qualities due to training and practice (acquirement) of the parents; 
that is, the best offspring (from the sportsman breeder’s point of 
view) come from the best trained parents. There is a great deal 
of ammunition for the advocates of Lamarckism in Redfield’s 


306 DARWINISM TO-DAY. 


records, although his too sharp distinction between structural and 
functional (so-called “dynamic”) characters is not at all helpful. 

The most recent serious treatment of the problem from the neo- 
Lamarckian side, and one of great interest and real force, is that 

Montgomery's of Montgomery in his book on “The Analysis of 
explanation of | Racial Descent in Animals’ (1906). Montgomery 
inheritance of contends that there can be no congenital variation: 
Varlation. without external: stimuli (or hybridisation) to initiate 
it, because germ-plasm cannot be assumed to set up change inde- 
pendently and automatically, as this would be almost like the 
assumption of spontaneous generation. Montgomery says, ““When 
the process of heredity proceeds unchanged the ontogeny of one 
individual is just like that of its parent. When a change of the 
ontogeny occurs, so that the offspring comes to be different from 
its parent, we say that a variation has appeared in the offspring. 
This variation, it is thinkable, may have been produced: (1) by 
internal growth energies, (2) by external environmental influences, 
or (3) by a combination of both; and it is necessary to discuss. 
which one of these is the most probable. 

“There is clearly, in the process of production of variation and. 
mutation, some modification of the normal process of heredity. 
Since in a number of species it has been shown that all the adult 
individuals from one locality are not exactly alike, but show meas- 
urable differences in dimensions, colour, or some other character, 
it follows that the hereditary process of each such individual must 
vary correspondingly, even though the variation does not become 
perceptible until the stage of maturity. The origin of inherited 
variation or mutation is then a question of the origin of modifica- 
tion of the hereditary process. 

“The regularity of the process of heredity is quite comprehensi- 
ble on the basis of the direct transmission of definite chromosomes 
in number, form, and quality constant for the species. From cell 
to cell, from individual to individual, these chromosomes are regu- 
larly transmitted in a continuous progress, therefore a succession of 
similar individuals is quite understandable. One germ-cell comes 
from a preceding one, to our knowledge is never formed from a 
specialised tissue-cell, so that there is an uninterrupted passage of. 
the germ-plasm through the race. This is Weismann’s idea of the 
continuity of the germ-plasm, which we will paraphrase as the 
continuity of the chromosomes. 

““A variation to become inherited must then be referable to a 
modification of the energies of this germ-plasm. The germ-plasm 
is living substance of proved great importance in the metabolism of 
the cell. Though in a sense it appears, from microchemical re- 


OTHER THEORIES’ OF *SPECIES-FORMING; 3°7 


searches, to be the chief agent in constructive processes of the cell, 
it equally appears to be incapable of life, or unable to act in a 
normal manner, when removed from the influence of other cell 
substances. The food required by a germ-cell for its growth is 
obtained from without the cell, and must pass through the cytoplasm, 
in more or less changed condition, to reach the chromatin within 
the nucleus and there be elaborated into living substance and 
passed over to the cytoplasm in other form. This conclusion is 
drawn from both experimental and microchemical studies. So the 
oxygen required by the cell, and the water, must be obtained from 
without the cell. This is simply in agreement with the general 
principle that no body can increase in mass, circumambient condi- 
tions remaining unchanged, without accretions from _ outside. 
Therefore, the germ-plasm does not so much create new substances 
as it changes substances brought to it. It and the other cell con- 
stituents are harmoniously and mutually interdependent, and the 
ultimate source of energies of these substances, all connected with 
the elaboration of living matter, is referable to external agencies 
because referable to food. 

“This being the case, the energies of the hereditable substance, 
the germ-plasm, are clearly dependent upon influences of the envi- 
ronment. This conclusion is not at all in contradiction with the 
idea of the continuity of the chromosomes, as we pointed out in 
the preceding chapter. Therefore, Weismann was in error when, to 
support his idea of the continuity of the germ-plasm, he at first 
argued the energies of the germ-plasm to be independent of body 
cells and of the environment generally. His supposition was both 
unnecessary for the view of the continuity, and also out of agree- 
ment with the phenomena. The ovum cannot elaborate its yolk 
substance except out of food substance received from without; 
the amount of its food substance will depend upon the state of 
nutritive metabolism of the individual carrying the egg-cell; starva- 
tion of that individual will cause cessation of energy in the germ- 
cell, and ligaturing of the blood-vessels supplying the ovary will 
produce death of the egg-cells. The results of observational expe- 
rience teach that the germ-plasm is not a little god, capable of self- 
existence without respect to external agencies, but is very intimately 
bonded to the latter. Whether the germ-cell, as in the sponges, be 
an amoeboid cell which wanders about in the body tissues, or 
whether it is immovably held in place by tissue-cells, it is impossi- 
ble that it can live and grow without receiving and reacting to 
stimuli from these tissue-cells. The egg-cells of many animals are 
set free in water before they commence to cleave into embryonic 
cells; how can we say, then, that the conditions in the water do 


308 DARWINISM TO-DAY. 


not influence them? They will die if removed from the water, and 
develop abnormally if certain substances be added to or subtracted 
from the water. But the embryonic differentiation is a result of 
chromosomal activities, as we have seen; therefore, changes in the 
medium must influence the germ-plasm. Is not a well-recognised 
characteristic of living matter, response to external stimuli? How 
can any living cell be acted upon by stimuli and yet not react to 
them? There is not a single observation to show that any germ- 
cell, or its germ-plasm, is in any way guarded or protected from 
external stimuli, either by the structure of its cell wall or peripheral 
cytoplasm, or by the nature of the living tissue that encloses it. 
And whatever affects the cell body must indirectly affect the 
‘chromosomes, because of the physiological connection of the two. 

“From such considerations it would seem practically certain that 
the energies of the chromosomes are to some extent respondent to 
environmental stimuli. And since observation shows that living 
matter responds differently, if not always according to the nature 
of the stimulus at least to its degree, it would follow that change in 
the nature or degree of the environmental agencies would indirectly 
engender change in the activities of the germ-plasm. Not to admit 
this would be to deny to the germ-plasm, without empirical reason, 
properties proven for all other living substances. 

“This thought had long ago been expressed clearly, though from 
a different line of reasoning, by Spencer (1865). We may state it 
in another way. Tuissue-cells are granted by experimental physiolo- 
gists the ability of different response, or different intensity of 
response, to stimuli of different kind or degree. But a tissue-cell 
is a lineal descendant of a germ-cell, and receives germ-plasm 
from the latter. Now since the germ-plasm has been transmitted 
continuously to the tissue-cell, must not the energies of the germ- 
plasms of the two be alike at least in their general response 
activity? Again, a Protozoan may be considered as a cell not 
exactly correspondent to a germ-cell of a Metazoan, but as some- 
thing more, as a unit with properties of both a germ-cell and a 
tissue-cell, for its cytoplasmic differentiations (cilia, contractile 
vacuoles, cytopharynx, etc.) are comparable to the soma of a Meta- 
zoan. In the case of the Protozoan Paramecium, Calkins (1904) 
has shown that the reproductive activity is increased or diminished 
according to the amount and kind of food stimuli. Here, then, a 
Protozoan has its reproductive activities, therefore the energies of 
its germ-plasm, profoundly influenced by environmental changes; 
and it is primarily what we may term the germ-cell constituent of 
the Protozoan that becomes influenced, that part which has to do 
with reproduction of the individual. Weismann considered the 


OTHER THEORIES OF SPECIES-FORMING., 309 


Protozoan exactly comparable, in the sense of strict continuity of 
reproduction, to the germ-cell of a Metazoan, and yet failed to 
note that a Protozoan can be influenced by environmental change. 

“Accordingly, an environmental change may be capable of induc- 
ing change in the energies of the germ-plasm. The expression of 
the energies of this substance, as viewed in temporal succession, 
constitutes heredity. Therefore, the process of heredity may become 
modified by a change in the environmental conditions of the germ- 
plasm. And since we defined variation as a modification of heredity, 
a variation could be produced by external influences acting upon 
the germ-plasm, understanding by external influences influences of 
the tissue-cells upon the germ-cells, or, in case the germ-cells are 
not enclosed, influences of the non-living environment.” 

In a recent exhaustive paper by Tower, W. L., on “Evolution in 
Chrysomelid beetles of the genus Leptinotarsa,’ Publication No. 48 
of the Carnegie Institution of Washington, 1907, the author, although 
on the whole a strong adherent of selection as the all-important 
factor in species-forming, states specifically his belief, on the basis 
of extensive observation and experiment, that external factors may 
and do influence the germ-plasm to the extent of compelling it to 
produce variations. These variations will not be photographic re- 
productions of modifications of the soma, but they will be the vari- 
ations which lie at the basis of species change. In other words, 
Tower holds that variations are epigenetic in their origin, although 
they are manifest as congenital differences. That is, acquired 
characters in the usual sense of the term are not heritable, but all 
variability is nevertheless due to the influence of environment. This 
paper by Tower is a distinctly valuable contribution to our knowl- 
edge of heredity and species change and it is based upon a are 
amount of actual close observation and experiment. 

In a recent paper by Jonathan Wright, “The Origin and Heredity 
of Matter,” in the St. Louis Medical Review, 1906, something of the 
same attitude is taken, although the author is much more inclined 
to the belief in the general heritability of acquired characteristics. 
This short paper is an admirable treatment, based on a full acquaint- 
anceship with the modern literature on the subject, of the problem 
of heredity. 

* See exposition of a number of these theories in appendix of 
chapter viii of this book. 

*Haacke, W., “Grundriss der Entwicklungsmechanik,”’ p. 289 
erate tre 

* Plate, L., “Uber die Bedeutung der Darwin’schen Selections- 
prinzip,” p. 218, 1903. 

* The following account of the scientific aspects of Luther Bur- 


310 DARWINISM TO-DAY. 


bank’s work, which has attracted so much attention from evolu- 
tionists and the world generally, was published by Kellogg, in the 
Pop. Sci., Mo., Vol. LXIX, pp. 363-374, 1906. 

“Mr. Burbank has so far not formulated any new or additional 
laws of species-change, nor do his observations and results justify 


Scientific any such formulation, and we may rest in the belief 
aspects of Bur- that he has no new fundamental laws to reveal. He 
bank's work, has indeed the right to formulate, if he cares to, some 


valuable and significant special conclusions touching certain already 
recognised evolution factors, in particular the influence on varia- 
bility of the two long-known variation-producing factors of hybridi- 
sation and modification of environment. His reliance on the marked 
increase in variability to be got after a crossing in the second and 
third generations over that obvious in the first, will come as a sur- 
prise to most men first getting acquainted with his work. He has 
got more starts for his new things from these generations than in 
any other way. He is wholly clear and convinced in his own mind as 
to the inheritance of acquired characters; ‘acquired characters are 
inherited or I know nothing of plant life,’ he says; and also con- 
vinced that the only unit in organic nature is the individual, not 
the species; that the so-called species are wholly mutable and de- 
pendent for their apparent fixity solely on the length of time through 
which their so-called phyletic characters have been ontogenetically 
repeated. He does not agree at all with de Vries that mutations in 
plants occur only at certain periodic times in the history of the 
species, but rather that, if they occur at all, they do so whenever 
the special stimulus derived from unusual nutrition or general 
environment can be brought to bear on them. He finds in his 
breeding work no prepotency of either sex as such in inheritance, 
though any character or group of characters may be prepotent in 
either sex. He believes that no sharp line can be drawn between the 
fluctuating or so-called Darwinian variations and those less usual, 
large, discontinuous ones called sports. Ordinary fluctuating varia- 
tion goes on under ordinary conditions of nutrition, but with ex- 
traordinary environmental conditions come about extraordinary 
variation results, namely, discontinuous, sport or mutational varia- 
tion. These variations are the effects of past environment also, 
having remained latent until opportunity for their development 
occurs. Starvation causes reversions, but reversions can also be 
produced by unusually rich nutrition. New variations are developed 
most often, as far as environmental influences go, by rich soil and 
generally favourable conditions. So-called new qualities are usually, 
if not always (the fact may sometimes not be obvious), simply 
new combinations of old qualities, both latent and obvious. To get 


OTHER THEORIES OF SPECIES-FORMING. git 


a new and pleasing odour it may often be sufficient simply to lose 
one bad element in an old odour. So one might go on for some 
pages with specific conclusions or deductions reached by Burbank 
on a basis of experience. But it is true that he has at his command 
the knowledge of no new fundamental scientific principles to give him 
advantage over us. And yet none of us has done what Burbank 
has been able to do, although many of us have tried. What then 
is it that Burbank brings to his work of modifying organisms 
swiftly and extremely and definitely that others do not? 

“To answer this it will be advisable to analyse in general terms, 
at least, the various processes which either singly, or in combina- 
tions of two or three, or all together, are used by Mr. Burbank in 
his work. We may roughly classify these processes and means. 
First, there is the importation from foreign countries, through 
many correspondents, of a host of various kinds of plants, some 
of economic value in their native land and some not, any of which 
grown under different conditions here may prove specially vigorous 
or prolific or hardy, or show other desirable changes or new quali- 
ties. Among these importations are often special kinds particularly 
sought for by Burbank to use in his multiple hybridisations; kinds 
closely related to our native or to already cultivated races which, 
despite many worthless characteristics, may possess one or more 
particular, valuable ones needed to be added to a race already useful 
to make it more useful. Such an addition makes a new race. 

“Second, the production of variations, abundant and extreme, by 
various methods, as (a) the growing under new and, usually, more 
favourable environment (food supply, water, temperature, light, 
space, etc.) of various wild or cultivated forms, and (b) by hybridi- 
sations between forms closely related, less closely related and, 
finally, as dissimilar as may be (not producing sterility), this 
hybridising being often immensely complicated by multiplying 
crosses, 7. e., the offspring from one cross being immediately crossed 
with a third form, and the offspring of this with still another form, 
and so on. These hybridisations are made sometimes with very 
little reference to the actual useful or non-useful characteristics of 
the crossed parents, with the primary intention of producing an 
unsettling or instability in the heredity, of causing, as Burbank 
sometimes says, ‘perturbations’ in the plants, so as to get just as 
wide and as large variation as possible. Other crosses are made, 
of course, in the deliberate attempt to blend, to mix, to add together, 
two desirable characteristics, each possessed by only one of the 
crossed forms. Some crosses are made in the attempt to extin- 
guish an undesirable characteristic. 

“Third, there is always immediately following the unusual produc- 


ZiL2 DARWINISM TO-DAY. 


tion of variations, the recognition of desirable modifications and the 
intelligent and effective selection of them, 1. e., the saving of those 
plants to produce seed or cuttings which show the desirable varia- 
tions and the discarding of all the others. In Burbank’s gardens 
the few tenderly cared for little potted plants or carefully grafted 
seedlings represent the surviving fittest, and the great bonfires of 
scores of thousands of uprooted others, the unfit, in this close 
mimicry of Darwin and Spencer’s struggle and survival in nature. 

“It is precisely in this double process of the recognition and selec- 
tion of desirable variations that Burbank’s genius comes into 
particular play. Right here he brings something to bear on his 
work that few other men have been able to do. It is the extraordi- 
nary keenness of perception, the delicacy of recognition of desirable 
variations in their (usually) smail and to most men imperceptible 
beginnings. Is it a fragrance that is sought? To Burbank in a bed 
of hundreds of seedling walnuts scores of the odours of the plant 
kingdom are arising and mingling from the fresh green leaves, but 
each, mind you, from a certain single seedling or perhaps from a 
similar pair or trio. But to me or to you, until the master prover 
points out two or three of the more dominant single odours, the 
impression on the olfactories is simply (or confusedly) that of one 
soft elusive fragrance of fresh green leaves. Similarly Burbank 
is a master at seeing, and a master at feeling. And besides he has 
his own unique knowledge of correlations. Does this plum seed- 
ling with its scores of leaves on its thin stem have those leaves 
infinitesimally plumper, smoother or stronger, or with more even 
margins and stronger petiole, or what not else, than any other 
among a thousand similar childish trees? Then it is saved, for 
it will bear a larger, or a sweeter, or a firmer sort of plum, or more 
plums than the others. So to the bonfires with the others and to 
the company of the elect with this ‘fittest’ one. Now this recogni- 
tion, this knowledge of correlations in plant structure, born of the 
exercise of a genius for perceiving through thirty years of oppor- 
tunity for testing and perfecting it, is perhaps the most important 
single thing which Burbank brings to his work that other men do 
not (at least in such unusual degree of reliability). Enormous 
industry, utter concentration and single-mindedness, deftness in 
manipulation, fertility in practical resource, has Burbank—and so 
have numerous other breeders and experimenters. But in his per- 
ception of variability in its forming, his recognition of its possi- 
bilities of outcome, and in his scientific knowledge of correlations, 
a knowledge that is real, for it is one that is relied on and built on, 
and is at the very foundation of his success, Burbank has an 
advantage of true scientific character over his fellow workers, and 


OTHER THEORIES OF SPECIES-FORMING. 313 


in it he makes a genuine contribution to scientific knowledge of 
plant biology, albeit this knowledge is so far only proved to be 
attainable and to exist. It is not yet exposed in its details and may 
never be, however unselfish be the owner of it. For the going 
to oblivion of scientific data of an extent and value equivalent, I 
may estimate roughly, to those now issuing from any half-dozen 
experimental laboratories of variation and heredity, is the crying 
regret of all evolution students acquainted with the situation. The 
recently assumed relations of Mr. Burbank to the Carnegie Insti- 
tution are our present chief hope for at least a lessening of this. 
loss. 

“But let us follow our saved plum seedling. Have we now to 
wait the six or seven years before a plum tree comes into bearing 
to know by actual seeing and testing what new sort of plum we 
have? No; and here again is one of Burbank’s contributions (not 
wholly original to be sure, but original in the extent and perfection 
of its development) to the scientific aspects of plant-breeding. This 
saved seedling and other similar saved ones (for from the exami- 
nation of 20,000 seedlings, say, Burbank will find a few tens or 
even scores in which he has faith of reward) will be taken from 
their plots and grafted on to the sturdy branches of some full-grown 
vigorous plum tree, so that in the next season or second next our 
seedling stem will bear its flowers and fruits. Here are years saved. 
Twenty, forty, sixty, different seedlings grafted on to one strong 
tree (in a particular instance Burbank had 600 plum grafts on a 
single tree!) ; and each seedling-stem certain to bear its own kind 
of leaf and flower and fruit. For we have long known that the 
scion is not materially influenced by the stock nor the stock by 
the scion; that is not modified radically, although grafting sometimes 
increases or otherwise modifies the vigour of growth and the extent 
of the root system of the stock. 

“Tf now the fruit from our variant seedling is sufficiently desira- 
ble; if it produces earlier or later, sweeter or larger, firmer or more 
abundant, plums, we have a new race of plums, a ‘new creation’ to 
go into that thin catalogue of results. For by simply subdividing 
the wood of the new branch, i. e., making new grafts from it, the 
new plum can be perpetuated and increased at will. Simple, is it 
not? No, it is anything but that in the reality of doing it; but in 
the scientific aspects of it, easily understandable. 

“Perhaps it may not be amiss to call attention to what must be 
the familar knowledge of most of us, and that is the fact that many 
(probably most) cultivated plants must be reproduced by division, 
that is by cuttings, buds, or grafts, and not by seeds, in order to 
grow ‘true. For a piece of a cultivated plant will grow out to be 


314 DARWINISM TO-DAY. 


very much like the individual it was cut from, but the seeds will 
not, in most cases, reproduce faithfully the parents, but will pro- 
duce a very variable lot of individuals, most of them strongly 
reversionary in character. Grow peach trees from the stones of 
your favourite peach and see what manner of peaches you get; 
but if you want to be sure of more peaches like the ones you enjoy, 
graft scions from your tree on to other trees. Indeed one of the 
plant-breeder’s favourite methods of making a start for new things, 
of getting the requisite beginning wealth and eccentricity of varia- 
tion, is to grow seedlings, especially from cross-bred varieties. 
Burbank will give you a thousand dollars for a pinch of horseradish 
seed. Sugar-cane seed is needed. The amelioration of many kinds 
of fruit and flowers and vegetables is checked, because in our care- 
lessness we have allowed these kinds to get into that condition of 
seedlessness which almost all cultivated races tend toward when 
grown from cuttings. In our oranges and grape-fruit and in a score 
of other fruits, the elimination of seeds is exactly one of the modifi- 
cations we have bred and selected for, in order to make the fruits 
less troublesome in their eating. But when we lose the seeds 
entirely of a whole group of. related plant kinds we may find our- 
selves, as we have found ourselves actually in many cases, at the 
end of our powers of amelioration of these plant sorts. Burbank 
believes that the very fact that plants when grown asexually always 
sooner or later lose their power to produce seeds is almost suffi- 
cient proof (if such proof is needed) that acquired characters are 
transmitted. 

“Another of Burbank’s open secrets of success is the great range 
of his experimentation—nothing is too bold for him to attempt, 
the chances of failure are never too great to frighten him. And 
another secret is the great extent, as regards material used, of each 
experiment. His beds of seedlings contain hundreds, often thou- 
sands, of individuals where other men are content with hundreds. 
Another element in his work is his prodigality of time. Experi- 
ments begun twenty years ago are actually still under way. 

“In all that I have so far written, I have purposely kept to gen- 
eral statements applicable to Burbank’s work as a whole. My 
readers might be more interested, perhaps, to have some illustra- 
tions of the application of various processes of making new sorts 
of things, some analytical account of the history of various specific 
‘new creations, but considerations of space practically forbid this. 
Just a few briefly described examples must suffice. More than is 
generally imagined, perhaps, Burbank uses pure selection to get 
new things. From the famous golden orange coloured California 
poppy (Escholtzia) he has produced a fixed new crimson form by 


OTHER - THEORIES OF (SPECIES-FORMING, SHS 


selection alone. That is, noticing, somewhere, sometime, an Escholt- 
ia individual varying slightly redder, he promptly took posses- 
sion of it, raised young poppies from its seeds, selected from among 
them those varying in a similar direction, raised new generations 
from them and so on until now he who wishes may have his 
California poppies of a strange glowing crimson for the price of a 
little package of seed. where formerly he was perforce content 
with the golden orange. For me the golden orange suffices, but 
that does not detract from my eager interest in the flower-painting 
methods of Mr. Burbank. Even more striking a result is his blue 
Shirley poppy, produced also solely by repeated selection from 
the crimson field poppy of Europe. ‘We have long had various 
shades of black and crimson and white poppies, but no shade of 
blue. Out of 200,000 seedlings I found one showing a faintest trace 
of sky blue and planted the seed from it, and got next year one 
pretty blue one out of many thousand, and now I have one almost 
pure blue.’ 

“But another brilliant new poppy was made in a different way. 
The pollen of Papaver pilosum, a butter-coloured poppy, was put 
on the pistils of the Bride, a common pure white variety of 
Papaver somniferum (double), and in the progeny of this cross was 
got a fire-coloured single form. The character of singleness was 
common to the ancestors of both parents, the character of fire colour 
in the lineage of somniferum only, although the red of the new 
form is brighter than ever before known in the somnifera series. 
Both characteristics were absent (or rather latent) in both parents. 
And yet the perturbing influence of the hybridisation brought to 
the fore again these ancestral characters. The foliage of this fire 
poppy is intermediate in type between that of the two parents. 

“The history of the stoneless and seedless plum, now being 
slowly developed by Burbanks, shows an interesting combination of 
selection, hybridisation, and reselecting. Mr. Burbank found a 
plum in a small wild plum species with only a part of a stone. 
He crossed this wild species with the French prune; in the first 
generation he got most individuals with whole stones, some with 
parts of a stone, and even some with no stone. Through three 
generations he has now carried his line by steadily selecting, and 
the percentage of no-stone fruits is slowly increasing, while quality, 
beauty, and productiveness are also increasing at the same time. 

“The plum-cot is the result of crossing the Japanese plum and the 
apricot. The plum-cot, however, has not yet become a fixed variety 
and may never be, as it tends to revert to the plum and apricot 
about equally, although with also a tendency to remain fixed, which 
tendency may be made permanent. 


316 DARWINISM TO-DAY. 


“Most of Burbank’s plums and prunes are the result of multiple 
crossings in which the Japanese plums have played an important 
part. Hundreds of thousands of seedlings have been grown and 
carefully worked over in the twenty years of experimenting with 
plums, and single trees have been made to carry as many as 600 
varying seedling grafts. The Bartlett plum, cross of the bitter 
Chinese Simoni and the Delaware, itself a Simoni hybrid, has the 
exact fragrance and flavour of the Bartlett pear. The Climax, a 
successful shipping plum, is also a cross of the Simoni and the 
Japanese triflora. This Chinese Simoni produces almost no pollen, 
but few grains of it ever having been obtained. But these few 
grains have enabled Burbank to revolutionise the whole plum 
shipping industry. The sugar prune, which promises to supplant 
the French prune in California, is a selected product of a second or 
third generation variety of the Petite d’Agen, a somewhat variable 
French pium. 

“Next in extent probably to Burbank’s work with plums and 
prunes is his long and successful experimentation with berries. 
This has extended through twenty-five years of constant attention, 
has involved the use, in hybridisations, of forty different species of 
Rubus, and has resulted in the origination of a score of new com- 
mercial varieties, mostly obtained through various hybridisations of 
dewberries, blackberries, and raspberries. Among these may spe- 
cially be mentioned the Primus, a hybrid of the western dewberry 
(R. ursinus) and the Siberian raspberry (R. crategifolius), fixed 
in the first generation, which ripens its main crop before most of 
the standard varieties of raspberries and blackberries commence to 
bloom. In this Primus berry, we have the exceptional instance of 
a strong variation, due to hybridisation, breeding true from the 
time of its first appearance. It usually takes about six generations 
to fix a new variety, but like de Vries’s evening primrose mutations, 
the Primus berry is a fixed new form from the time of its beginning. 
An interesting feature of Mr. Burbank’s brief account, in his ‘New 
Creations’ catalogue of 1804, of the berry experimentation, is a re- 
production of a photograph showing ‘a sample pile of brush, 12 
ft. wide, 14 ft. high, and 22 ft. long, containing 65,000 two- and 
three-year-old seedling berry bushes (40,000 blackberry \ rasp- 
berry hybrids and 25,000 Shaffer \ Gregg hybrids) all dug up 
with their crop of ripening berries. The photograph is introduced 
to give the reader some idea of the work necessary to produce a 
satisfactory new race of berries. ‘Of the 40,000 blackberry \ rasp- 
berry hybrids of this kind, “Phenomenal” is the only one now in 
existence. From the other 25,000 hybrids, two dozen bushes were 
reserved for further trial.’ 


OTHER THEORIES OF SPECIES-FORMING, © (317 


“An astonishing result of the hybridisation between the black 
walnut, Juglans nigra, used as the pistillate parent, and the Cali- 
fornia walnut, J. californica, staminate parent, are walnut trees 
which grow with such an amazing vigour and rapidity that they 
increase in size at least twice as fast as the combined growth of 
both parents. Many tremendous growers are got in the first gen- 
eration, but in the second there are included some of the most 
rapidly growing trees, perhaps, in the world. This hybrid has 
clean-cut, glossy bright-green leaves from two to three feet long 
with a sweet odour like that of apples, but it produces few nuts. 
Curiously enough the result of hybridisation by using the pollen 
of nigra on pistils of californica produces in abundance large nuts 
of a quality superior to that possessed by either parent. 

“The famous Shasta daisy is the result of a multiple crossing 
between an American and a European species of field daisy and 
then between these hybrids and a Japanese form. The fragrant 
calla, known as ‘Fragrance,’ is descended from a single individual 
found by Burbank while critically examining a block of Little Gem 
calla seedlings. He was surprised in this examination by a fra- 
grance resembing that of violets or water-lilies; as he had long 
been seeking a fragrant calla, the individual giving this perfume was 
carefully hunted out. No farther selecting was done; this plant 
was the single ancestor of the fragrant new race. 

“And so one might go on for pages, but with slight variations in 
detail all these pages would tell only the same story: the stimulating 
or inducing of variability by environmental influences and by hybrid- 
isations; the search after, and keen recognition of, promising spe- 
cial variations; the selection of the plants showing these variations ; 
rearing new generations from them, repeated selection, and new 
hybridisations to eliminate this characteristic or introduce that, 
and on until a desirable combination is found. Then the careful 
fixing of this form or type by repeated selection through several 
generations. 

“But an end must be made of this. Let us, in a paragraph, simply 
sum up the essential things in the scientific aspects of Burbank’s 
work. No new revelations to science of an overturning character; 
but the revelation of the possibilities of accomplishment, based on 
general principles already known, by an unusual man. No new laws 
of evolution, but new facts, new data, new canons for special cases. 
No new principle or process to substitute for selection, but a new 
proof of the possibilities of the effectiveness of the old principle. 
No new categories of variations, but an illuminating demonstration 
of the possibilities of stimulating variability and of the reality of 
this general variability as the fundamental transforming factor. 


318 DARWINISM TO-DAY. 


e 


No new evidence either to help the Darwinian factors to their death- 
bed, or to strengthen their lease on life; for the ‘man’ factor in all 
the selecting phenomena in Burbank’s gardens excludes all ‘natural’ 
factors. Here are some of Burbank’s own words, touching these 
matters that scientific men are particularly interested in, in his work: 

““All scientists have found that preconceived notions, dogmas, 
and all personal prejudice must be set aside, listening patiently, 
quietly, and reverently to the lessons one by one which mother 
nature has to teach, shedding light on that which before was a 
mystery, so that all who will may see and know. 

“Crossing gives the raiser of new plants the only means of 
uniting the best qualities of each, but just as often the worst quali- 
ties of each are combined and transmitted, so that to be of any 
value it must be followed by rigid and persistent selection, and in 
crossing, as in budding and grafting, the affinities can only be 
demonstrated by actual test. 

“All wild plants of any species are under almost identical envi- 
ronments, having their energies taxed to the utmost in the fierce 
struggle for existence. Any great variation under such circum- 
stances is not likely to occur, and is much more likely to be stamped 
out at once by its struggling competitors, unless the variation should 
be of special use in competition, in which case it will survive, and 
all others may be supplanted by it. Thus we see how new species 
are often produced by nature, but this is not her only mode. Crosses 
and hybrids are very often found growing wild where two some- 
what similar species grow contiguous, and if the combination hap- 
pens to be a useful one, as it often does, the new creation is 
encouraged by nature; then time and environment fix it, and man 
comes on the scene, perhaps ages later, and discovers it, and, not 
knowing all the facts, wonders where the connecting links have 
gone. It is botanically classified as a new species, which it is most 
certainly. . 

“Tn cultivated plants the life struggle is removed, and here we 
find variation almost the rule rather than the exception. 

“ “Varieties are the product of fixed laws, never of chance, and 
with a knowledge of these laws we can improve the products of 
nature, by employing nature’s forces, in ameliorating old and produc- 
ing new species and varieties better adapted to our necessities and 
tastes. Better food, more sunshine, less arduous competition, will 
of themselves induce variation in individual plants which will be 
more or less transmitted to their seedlings, which, selected con- 
secutively through a certain number of generations, will become 
permanent. Environment here exerts an influence as in all chemical 
cosmical, and celestial movements. These small increments from 


OTHER THEORIES OF SPECIES-FORMING. 31 


environmental forces may produce a gradual or sudden change 
according to circumstances. The combustion of food liberates the 
moving force, environment guides it as it does the planets. 

“When once the persistent type is broken up, old latent forces 
may be liberated and types buried in the dim past reappear. This, 
called atavism, is a concentration of ancestral forces—reverberating 
echoes—from varieties long since passed away, exhibiting them- 
selves when from some cause, for instance crossing, present forces 
are in a state of antagonism, division, perturbation, or weakness. 
These echoes, if collected by crossing and selection, produce com- 
binations of superlative importance and value.’ ” 

"Plate, L., “Uber die Bedeutung,” etc., p. 220. 

* See Koken, Ernst, ““Palzontologie und Descendenzlehre,” 1902. 
Koken (Professor of Geology and Palzontology in the University 

Orthogenetic Of Tubingen) is very explicit in the statements of his 
variation in belief that the paleontological records prove the exist- 
paleontology. ence of orthogenetic variation and hence evolution. 
“Das Darwin’sche Prinzip der Selektion ist nicht das einzige, das. 
in Betracht kommt und es scheint nicht das wichtigste zu sein. 
Vielfach vermissen wir in der paleontologischen Geschichte den 
Hinweis auf ein Eingreifen des Kampfes ums Dasein und anderer- 
seits heben sich Richtungen der Entwickelung heraus, welche ‘nicht 
in Beziehung zu einem Nutzen stehen, in einigen Fallen zu einer 
Schadigung der socialen Bedingungen fihren.” 

* For an account of the facts of one such case, see Kellogg, ‘Is 
There Determinate Variation,” Science, N. S., Vol. XXIV, pp. 621- 
628, 1906. In this paper the gradual but obvious change from. 

Acaseofap- One dominant type of colour-pattern to another in 
parent determi- the leaf-eating beetle Diabrotica soror (on the campus. 
nate variation. of Stanford University, California) during the last 
ten years, is shown by statistical variation studies. It is shown 
that such change is not explicable on a basis of intra-specific 
selection, nor can it be interpreted as a direct ontogenic reaction 
in each succeeding generation to changing climatic conditions. The 
case is believed to be an example of definitive orthogenetic: 
variation. 

Certain examples of presumable determinate variation have been 
recorded by Henslow (“The Origin of Species,” Natural Science, 
p. 250, 1894). ‘In 1847, Prof. J. Buckman sowed seed of wild 
parsnip in the garden of the Agricultural College, at Cirencester. 
The seedlings began to vary, but in the same way, though in differ- 
ent degrees. By selecting seed from the best rooted plants, the 
acquired ‘somatic’ characters of an enlarged root, glabrous leaves, 
etc., became fixed and hereditary; and ‘The Student,’ as he called 


329 DARWINISM TO-DAY. 


it, having been ‘improved’ by Messrs. Sutton & Sons, is still 
regarded as ‘the best in the trade.’ This is definite variation, ac- 
cording to Darwin’s definition, for those weeded out did not differ 
from the selected, morphologically, except in degree, the variations 
towards improvement not being quite fast enough to entitle them 
to survive. 

“M. Carriére raised the radish of cultivation, Raphanus sativus, 
L., from the wild species R. raphanistum, L., and moreover found 
that the turnip-rooted form resulted from growing it in a heavy 
soil, and the long-rooted one in a light soil.* Pliny records the 
same fact as practised in Greece in his day, saying that the ‘male’ 
(turnip form) could be produced from the ‘female’ (long form), by 
growing it in ‘a cloggy soil.’ Both forms are now, of course, 
hereditary by seed.” 

*® Nageli, C. von, ‘“Mechanisch-physiologische Theorie der Ab- 
stammungslehre,” 1884. 

** Korschinsky, S., “Heterogenesis und Evolution,” Naturwiss. 
Wochenschrift, Vol. XIV, pp. 273-278, 1800. 

** Recently, Georg Pieffer (“Die Entwicklung,’ 1895) has pro- 
posed a theory of orthogenetic evolution not very different from 
the much earlier Nagelian one. Pfeffer postulates as 
inherent in living matter a capacity for change and 
for self-directing this change. The principle of 
change or progress he calls the conception of ““developmental-screw” 
(Entwicklungsschraube), and for directing this progress the con- 
ception of “‘self-steering” (Selbststeuerung). Both these capacities 
of individualised living stuff are something over and beyond the 
mechanical and physico-chemical attributes of living matter. “On 
the contrary,’ says Pfeffer, “life consists of the capacity (more 
exactly the exercise of this capacity) of consciously permitting and 
consciously influencing (that is, actually producing) through 
physico-chemical phenomena changes in the matter or form of the 
fundamental life-stuff.” 

From this curious, though keen, critical, and constructive essay, 
I quote as follows: 

“Der Begriff der Entwickelungsschraube deckt sich eigentlich 
vollig mit dem Begriff der Selbststeuerung der lebendigen Natur; 
ich halte aber mit gutem Grunde beide Ausdriicke aufrecht, weil 
sie einer verschiedenen Betrachtung entspringen, namlich die 
Selbststeuerung der mechanischen, die Entwickelungsschraube der 
historischen, entwickelungsgeschichtlichen Betrachtungsweise; die 
Selbststeuerung ist das Prinzip der Herstellung des Gleichgewichtes 


* This has been corroborated by M. Languet with the carrot. Soc. 
Roy. et Cent. d’Agricult., 2d ser., Vol. II, 1846-7, p. 539. 


Pfeffer’s theory 
of orthogenesis, 


OTHER THEORIES OF SPECIES-FORMING. 321 


eines aus lebendigen Einheiten gebildeten Ganzen; die Entwickel- 
ungsschraube das Prinzip der veranderten Weiterfuhrung dieser 
Gleichgewichtsverhaltnisse in der Zeit. Also ist, ebenso wie die 
Selbststeuerung, auch die Entwickelungsschraube selbstthatig (pp. 
E2iand 13), 

“Es ist hier nicht der Ort, die physikalischen wie die Unzahl der 
‘chemischen Eigenschaften der lebendigen Grundsubstanz zu er6r- 
tern; sie liegen freilich nicht auf der Hand, sind aber im Ganzen 
ziemlich leicht herzuleiten als das allen lebendigen protoplasmati- 
schen Substanzen Gemeinsame. Es fallt aber Niemandem ein, bez. 
sollte Niemandem einfallen, die physikalischen und chemischen 
Eigenschaften der lebendigen Substanz als Lebens-Eigenschaften zu 
betrachten; vielmehr besteht das Leben in der Fahigkeit (bez. der 
Austibung der Fahigkeit),: die durch chemisch-physikalische 
Vorgange an dem Stoff oder der Form-Auspragung der Grund- 
substanz bewirkten Veranderungen bewusst zu erleiden und bewusst 
zu beeinflussen (bez. hervor zu bringen). Es hat also jeder kor- 
perliche Vorgang der lebendigen Substanz seinen von ihm untrenn- 
baren Bewusstseinsvorgang; oder anders ausgedruckt: jeder Vor- 
gang an lebendigen Wesen hat einen in chemisch-physikalische und 
einen anderen in Bewusstseins-Verhaltnisse zerlegbaren Anteil. 
Beide sind Gegenstande wissenschaftlicher Betrachtung, dagegen 
entzieht sich die Art und Weise des Zusammenhanges zwischen 
beiden unserm Anschauungsvermogen, liegt also ausserhalb der 
naturwissenschaftlichen Betrachtung und ist damit als gegeben 
hinzunehmen’”’ (p. 17). 

A recent proposal of an orthogenetic theory of the general 
character of Nageli’s is that set out in O. F. Cook’s “Aspects of 
Kinetic Evolution,” Proc. Wash. Acad. Sci., Vol. VIII, pp. 197-403, 
1907. 

** Eimer, Th., “Die Entstehung der Arten auf Grund von Verer- 
bung erworbener Eigenschaften nach den Gesetzen organischen 
Wachsens,” I, 1888; trans. into English, as “Organic 
Evolution,” 1889; ‘“‘Artbildung und Verwandschaft 
bei den Schmetterlingen,” I, 1889, II, 1895; ‘“Ortho- 
genesis bei Schmetterlinge” (Part II of “Die Entstehung der 
Arten’”), 1898; ‘‘Orthogenesis,’ 3 Internat. Congress Zool., 1895; 
trans. in English as “On Orthogenesis and the Impotence of Natural 
Selection in Species-Formation,” 1898. This address, and Eimer’s 
other writings as well, are sadly marred by intemperate polemic 
and the indulgence of personal rancor. He deems himself and his 
views unfairly overlooked by biologists and seems to hold Weismann 
personally responsible for this. Apart from these unfortunate 
digressions his papers are extremely suggestive and logically and 


Eimer’s theory 
of orthogenesis. 


322 DARWINISM TO-DAY. 


keenly composed. I believe that Eimer’s work and theories should 
have more attention from students of evolution then they now get. 

** Dean, Bashford. ‘Evolution in a Determinate Line, as IlJlus- 
trated by the Egg-Cases of Chimzroid Fishes,” Biol. Bull., Vol. 

Apparent deter- VII, pp. 105-112, 1904. In this paper the author 
minate evolution. expresses his belief that the conditions existing in the 
curious inter-related adaptations between eggs and egg-cases of the 
shark-like fish, Chimera, can be explained only on the basis of 
determinate or orthogenetic modifications, in which modifications 
neither natural selection nor the Lamarckian factors of use and 
disuse can have played any part. The capsule or egg-case, although 
“only indirectly connected with the egg, 7.e., as a secretion formed 
by the parent after the mechanism of heredity has already been 
established in the egg, nevertheless foresees with startling exact- 
ness the size and shape of the young fish when many months hence 
it comes to hatch out, and it provides a series of progressive multi- 
plications adapted to the physical needs of the young. It 1s evident, 
accordingly, that if natural selection be adduced to explain the 
present phenomena it encounters difficulties more numerous and 
complex than in usual instances. In the latter cases selection con- 
cerns itself with variations which affect the progeny directly; but 
in the present case variations must have occurred in the lines both 
of the progeny and, indirectly, of its far less indifferent capsule- 
forming capabilities—with result that a succession of closely corre- 
lated stages in variation must have coincided in both distinct con- 
ceptions.” 

® Plate, L., “Uber die Bedeutung,” etc., p. 190 ff. 

*® Rosa, Daniel, “La Riduzione Progressiva della Variabilita i 
suoi Rapporti coll’ Estinzione e coll’ Origine della Specie,” 1899. 
Author believes that in animal life there is a gradual progressive 
reduction of variation (or modification) necessitated by the well- 
known fact that highly specialised forms have distinctly fewer lines 
of modification, 7. e. specialisation, left open to them than general- 
ised forms; and that all groups of animals are of the nature of 
series of more and more specialised forms. He bases this belief, as 
far as facts go, on the well-known cases of the dying out of spe- 
cialised species (Irish stag) and specialised groups (Cretaceous 
reptiles), and on the alleged facts (which the author devotes many 
pages to trying to show) that all present-day principal groups of 
animals are related to each other solely by derivation from com- 
mon very old and generalised ancestors. If there is less modifica- 
tion possible, then there occurs actually less and less variability, and 
the actually occurring variations will be only along certain lines, 
a. e. there will be in this limited variability an actual basis for ortho- 


OTHER THEORIES OF SPECIES-FORMING. 323 


genesis. On the double basis of progressively less variation and of 
the thus produced orthogenesis the author sees a factor in phylogeny 
(organic evolution) which works, to some degree, independently of 
natural selection or of Lamarckian factors. Rosa thinks he has 
thus contributed to biology one of the always sought-for “unknown 
factors in evolution.” 

‘7 Tn an interesting paper by Snodgrass, ‘“‘The Relation of the Food 
to the Size and Shape of the Bill in the Galapagos Genus Geospiza,”’ 

Snodgrass's 4k, Vol. XIX, pp. 367-381, 1902, detailing the ex-~ 
observations on amination of the stomach contents of over 200 indi- 
bills of Gala- viduals, representing 13 species and sub-species (taken 
pagos birds, from several of the Galapagos Islands) of the peculiar 
Galapagos Fringillid genus, Geospiza, remarkable for the great 
differences in size and shape of bill characterising the various 
species and sub-species, the author states that all the “evidence 
seems to be in favour of the general conclusion that there is no 
correlation between the food and the size and shape of the bill.” 
The following five propositions were established: (1) The same 
species at different localities may feed on different seeds; (2) 
different species at the same locality may feed on the same kinds 
of seeds; (3) different species at different localities may feed on 
the same kinds of seeds; (4) different species at the same or at 
different localities may feed on different seeds; and (5) birds 
with small bills eat only small seeds; birds with large bills eat both 
small and large seeds. The seeds taken from the stomachs varied 
in size from seeds of I cubic millimetre up to those 15 mm. long 
by 10 mm. thick. The bill of the different species and sub-species 
of Geospiza, varies from that of G. scandens scandens, 13 mm. 
long by 7 mm. high at base, to that of G. pachyrhyncha, 17 mm. 
long by 20 mm. high at base. 

** Eimer, Th., “Orthogenesis der Schmetterlinge,” 1897. < 

** Cope, E. D., “The Method of Creation of Organic Types,” 
Proc. Amer. Phil. Soc., December, 1871. 

*° Cope, E. D., “The Energy of Life Evolution,” Pop. Sct. Mo., 
Vol. XXVII, pp. 789-800, October, 1885: “Primary Factors of 
Organic Evolution,” 1896. 

*2 “Palzontologists, as a rule——and Prof. Cope is one of them,— 
are so profoundly impressed by the adaptive nature of the evolu- 

Cope’s belief tionary process and by the definitiveness of its direc- 
in orthogenetic tion, that they cannot regard the restraining or 
evolution, selective action of the environment as enough to keep 
the breed true. They are so accustomed to seeing mutation after 
mutation, generation after generation, developing in apparent obe- 
dience to obvious physico-chemical or mechanical conditions, that 


324 DARWINISM TO-DAY. 


they incline to regard these conditions as causes. And if it be 
suggested to them that the results they see may have been achieved 
by the selection of adaptive variations from among a number of 
promiscuous variations that are not adaptive, they ask why it is 
that they do not find evidence of these numerous known adaptive 
variations in the organs, when one would suppose that, on any 
hypothesis, except that of definite variation, such forms must have 
been the more abundant of the two. It is useless to reply to them 
that the known adaptive variations in each generation were killed off 
when young, and so, even if fossilised, are practically undistinguish- 
able; because they will reply with abundant proof that the adaptive 
characters chiefly appear in the adult stages of the organism, possibly 
only in its senile stages, and so are incapable of coming under 
the action of natural selection during the early undifferentiated 
stages. How the conversation might continue does not much 
matter, for it is obvious that it has reached a point beyond which all 
must be speculation. The facts on which the paleontologist relies, 
the facts that Prof. Cope adduces with such wealth of knowl- 
edge, are strong presumptive evidence in favour of his second 
thesis, but they are not proof.” (Bather, F. A., Natural Science, 
Vol. X, pp. 40-41, 1897.) 

Prof. Scott, another American paleontologist, discusses the 
question of variation in an interesting paper in the American Journal 
of Science, Vol. XLVIII, pp. 335-374, 1894. The great point made 
by Prof. Scott is the clear distinction between individual and 
phylogenetic variation. Individual variation is irregular and not 
fixed, while “phylogenetic variation,” or mutation (in the sense of 
* Waagen) which is distinguished from individual variation, not 
by any character of quantity or quality, but by pursuing sie 
minate direction and thus, under control of natural selection, leading 
to the formation of new species. “Remembering that the signifi- 
cant fact in the history of a group is not so much the character of 
its variations at any one stage, as the gradually shifting positions 
successively occupied by the normal or centre of stability, we find 
that any mammalian series at all complete, such as that of the 
horses, is remarkably continuous, and that the progress of discovery 
is steadily filling up what few gaps remain. So closely do successive 
stages follow upon one another that it is sometimes extremely 


* The term “mutation” was first used in biology, probably, by 
Waagen, 1869, in a paper on the phylogeny of an ammonite. In 
this first use of the word its meaning was a change or modification 
accomplished during a considerable historic period. Indeed, it had 
much the meaning of evolution or descent as we use these terms 
nowadays. 


OTHER THEORIES OF SPECIES-FORMING.,. 325 


difficult to arrange them all in order and to distinguish clearly 
those members which belong in the main line of descent, and those 
which represent incipient branches. Some phylogenies actually 
suffer from an embarrassment of riches.” 

2? Whitman, C. O., “The Problem of the Origin of Species,” Pro- 
ceedings of Congress of Arts and Science, Universal Exposition, St. 

Wiitman’s Louis, Vol. V, pp. 41-58, 1906. In this paper Whit- 
belief in deter- man takes strong ground for orthogenesis and recites 
minate variation. jn detail a number of interesting facts touching the 
evolution of pattern in pigeons to illustrate his belief. Touching 
the criticism of orthogenesis, that it involves a teleologic element 
in its make-up, Whitman says (p. 5): “I take exception here only 
to the implication that a definite variation-tendency must be con- 
sidered to be teleologic because it is not ‘orderless.’ I venture to 
assert that variation is sometimes orderly, and at other times rather 
disorderly, and that the one is just as free from teleology as the 
other. In our aversion to the old teleology so effectually banished 
from science by Darwin we should not forget that the world is 
full of order, the inorganic no less than the organic. Indeed, what 
is the whole development of an organism if not strictly and marvel- 
lously orderly? Is not every stage, from the primordial germ on- 
ward, and the whole sequence of stages, rigidly orthogenetic? If 
variations are deviations in the directions of the developmental 
processes, what wonder is there if in some directions there is less 
resistance to variation than in others? What wonder if the organ- 
ism is so balanced as to permit of both unifarious and multifarious 
variations? If a developmental process may run on throughout 
life (e. g., the life-long multiplication of the surface-pores of the 
lateral-line system in Amia), what wonder if we find the whole 
species gravitating slowly in one or a few directions? And if 
we find large groups of species, all affected by a light variation, 
moving in the same general direction, are we compelled to regard 
such ‘a definite variation-tendency’ as teleological, and hence out 
of the pale of science? If a designer sets limits to variation in 
order to reach a definite end, the direction of events is teleological ; 
but if organisation and the laws of development exclude some 
lines of variation and favour others, there is certainly nothing super- 
natural in this, and nothing which is incompatible with natural 
selection. Natural selection may enter at any stage of ortho- 
genetic variation, preserve and modify in various directions the 
results over which it may have had no previous control.” 

** Cunningham, an English neo-Lamarckian, expresses (“Origin 
of Species Among Flatfishes,’ Natural Science, Vol. VI, p. 239, 
1895) his belief in orthogenesis as follows: 


326 DARWINISM TO-DAY. 


“The only general view, as it seems to me, which can be held 

concerning the structural diversity of the animal kingdom, is to 
regard it as resultant of two more or less opposing 

Cunningham general tendencies. On the one hand, there is uni- 

and orthogenesis. : ; Aine 
versal evidence of a tendency to definite variation, or 

growth in different directions, leading to manifold variety of regu- 
lar definite symmetrical forms. This tendency can only be regarded 
as internal to the organism, as connected with a tendency to growth 
and multiplication inherent in’ organic units. On the other hand, 
there is the molding, limiting, constructing action of the external 
forces of the environment resulting in more or less complete adap- 
tation. Whatever be the process of adaptation, whether Darwinian 
selection or Lamarckian modification, adaptive structural combina- 
tions are mechanisms each working with the particular result which 
is important to the feeding, living, and breeding of the organism. 
Whatever the causes of non-adaptive variation, the resulting struct- 
ural features are the regular genetic forms and characters which the 
multitude of different organic forms present in such marvellous 
diversity. No one who, like Weismann, ignores everything except 
adaptation, or who, like Bateson, regards the study of adaptations 
as barren and profitless, can hope to produce a consistent and com- 
prehensive theory of organic evolution.” 

** Delage, Yves, “L’Hérédité,” 2d ed. p. 849, and others, 1903. 

*° Jaeckel, O., “Uber verschiedene Wege phylogenetischer Ent- 
wicklung,” I902. 


(ELA oc E har 


OTHER THEORIES OF SPECIES-FORMING AND 
DESCENT (CONTINUED): ALTERNATIVE 
THEORIES (CONTINUED). 


Heterogenesis—Under the name heterogenesis we have 
to consider a theory of species-forming which is more popu- 
larly and widely known under another name, viz., the muta- 
tions theory. This theory is commonly associated with the 
name of de Vries, the Amsterdam botanist. But this gen- 
eral conception of species-forming on a basis of the occur- 
rence of occasional, sudden, fixed, and often considerable 
changes or variations in the offspring of a plant or animal, 
_ is a conception not of course new with de Vries, but one 
variously expressed by numerous biologists from Dar- 
win’s time on, especially by von Kolliker, Galton, Dall, 
Bateson, Emery, Scott, and Korschinsky. It is, however, 
chiefly due to the patient, persistent, well-planned, and ex- 
tensive experiments and observations of de Vries that this 
theory of species-forming by heterogenesis, or as called by 
de Vries, by mutations, has recently received so much re- 
newed attention. With the observations of de Vries on the 
breeding of certain plant species, notably certain Cénotheras 
(evening primroses), there have been much associated in 
recent popular scientific literature accounts of the ear- 
lier observations of Gregor Mendel,’ an Augustinian monk, 
who recorded, in 1865, in an obscure journal, some very 
valuable observations and logical conclusions concerning the 
phenomena of heredity in certain other plants (especially 
garden peas). Reference should also be made, in this con- 

327 


328 DARWINISM TO-DAY. 


nection, to observations and experiments carried on nearly 
simultaneously with those of de Vries by Correns* and 
Tschermak.* As a matter of fact the data on which de 
Vries bases his theory of species-forming by heterogenesis 
are, in part, nearly identical with those obtained by Mendel, 
Tschermak, and Correns, which, however, is concerned 
primarily with explaining the “laws” of heredity. 

The meaning of heterogenesis in connection with species- 
forming and descent is essentially this: whereas by the 
Darwinian theory species are transformed slowly and by 
slight changes in at first one or two or a few and only 
later in more parts, and all new species are derived from the 
old ones (which usually disappear as the new ones appear) 


_by the gradual selection of the advantageous ones among the 


ie 


regular slight, fluctuating, individual variations (known 
commonly as Darwinian variations and which mostly occur 
according to the law of error), by the theory of hetero- 


| genesis new species appear suddenly, not by a selective 


variation, 


variations known as “sports, 


\choosing among the slight fluctuating Darwinian variations, 
but independently of selection, and largely independently of 


the so-called Darwinian variations, by the appearance in 
fixed definitive form of several to many slight to consider- 
able variations, which give the new species definite char- 
acteristics differentiating it often in many particulars from 
the old species, which differentiating characteristics are fully 
and faithfully transmitted to the succeeding generations of 
individuals derived from this suddenly born new species. 
In some theories or views of heterogenesis the suddenly 
appearing new variations—and none of these theories gives 
a satisfactory explanation of the cause of these 
sudden variations—which give rise to new 
species, are those large, sometimes monstrous, 
” “monsters,” etc.; or, in Bate- 
son’s words, are “discontinuous variations,” 7. e., considerable 
variations not connected by a continuous series of gradations. 


Discontinuous 


7 


OTHER THEORIES OF SPECIES-FORMING. 329 


with the parent type of the variable organ or individual. 
Darwinians have always been interested in such variations, 
for if they do occur in any considerable numbers they might 
offer a possible solution of that difficulty in the selection 
theory of explaining the origin of new structures and the 
needed degree of size and development sufficient to make 
these beginnings useful and hence available as handles for 
natural selection. But it has long been recognised that such 
sports or discontinuous variations are too few and occur too 
rarely to furnish the basis for a comprehensive theory of 
species-forming. Like the extremes of individuals in the — 
series of fluctuating variations, their characters would be 

lost or swamped by crossing. Darwin himself made as full ~ 
a list of such sports as any post-Darwinian writer, ex- 
cepting Bateson, has been able to do, and he recognised 
the fact that certain species, or races at least, of domesticated 
animals and cultivated plants undoubtedly had their begin- 
nings in these sports. His examples of such discontinuous 
or saltatory evolution as the Ancon and Mauchamp sheep, 
the Paraguay cattle,* etc., are the classic examples in ani- 
mal evolution, and to this day nearly the only ones! Bate- 
son” has, to be sure, gathered together in his “Materials. 
for the Study of Variation” a much larger list of sports or 
discontinuous variations than Darwin included in his knowl- 
edge (it should be borne in mind in referring to Bateson’s 
list that several, probably, indeed, many of his alleged ex- 
amples are cases of teratogenic regeneration)—but he has 
been able to add almost no new examples of the origin of 
a new species from such discontinuous variations. A few 
cases are known of the inheritance through a number of 
generations of suddenly appearing sports or discontinuous. 
variations in human beings (cases of polydactyly, etc.) and 
cats. (Kennel’s stump-tailed cat, which produced in six 
litters four stump-tailed, twelve tailless, and twelve normal 
young, is an example of several similar cases which have 





330 DARWINISM TO-DAY. 


been recorded.) Species-forming by sports and discon- 


| tinuous variations is obviously no theory to presume to 


offer itself as a species-forming substitute for natural selec- 
tion. But the de Vriesian mutations theory, the most 
recent development of the heterogenesis conception, has 
rehabilitated this conception to such an extent that a number 
of biologists see in it an actually satisfactory substitute for 
the natural selection theory. Before explaining the theory 
of de Vries let us first note two or three other prior formula- 
tions of theories of heterogenesis, one at least being nearly 
identical with that of de Vries. 

In 1864 the great zoologist von Kolliker,* in a paper under 
the title “Uber die darwinische Schopfungstheorie,”’ took 
positive ground against the adequacy oractuality 
of natural selection as a species-forming factor, 
and proposed a theory of “heterogene Erzeu- 
gung”’ (heterogenesis) which he formulated, however, only 
in most general terms. He said that “under the influence 
of a general law of development (evolution) organisms 
bring forth other kinds differing from them out of the 
germs produced by them.” He included in his general theory 
of heterogenesis a basic plan of progressive evolution. 
Such a conception has in it too much autogenic orthogenesis ; 


Von Kolliker’s 
suggestion. 


| it is too redolent of teleology for present-day biology. The 


variations, too, which are to serve as beginnings of new 
species are those too rare ones which we have referred to 
as sports and discontinuous variations. 
The American naturalist, Dall,’ in a paper written in 
1877, expresses his conviction that sudden changes of 
species-forming character do occur, and as- 
_ Dall’s belief cribes such changes “to the action of the 
in sudden spe- : : 
cies-change, law of development, which finds expression 
in the paradox that the same species may 
belong to different genera.” That sudden leaps may be 
due to the gradual accumulation of minute differences he 


ceenetnentns 


OTHER THEORIES OF SPECIES-FORMING. 331 


exemplifies as follows: “In a sloping gutter of a paved 
street not too cleanly swept every one will notice on a sudden 
shower how small particles of earth and other materials 
will sometimes act as a dam, producing a puddle which, 
relieved by partial draining, may for a time remain in 
statu quo. A time comes, however, when the gradually 
accumulated pressure suddenly sweeps the dam before it 
for a short distance, until another similar one is formed, the 
pool again appears for a time to remain unchanged, and 
so on indefinitely. Now the modern idea of a species may be 
stated to be a greater or lesser number of similar individual 
organisms in which for the time being the majority of 
characters are in a condition of more or less stable equi- 
librium, and which have the power to transmit these char- 
acters to their progeny with a tendency to maintain this 
equilibrium. This tendency may be, in some cases, sufficiently 
strong to resist for a considerable period the changes which 
a gradual modification of the environment may tend to bring 
about. When the latter has reached a pitch which renders 
the resistance no longer effectual, it is conceivable that a 
sudden change may take place in the arrangement of the 
constitution of the organism, adapting it once more to its 
surroundings, when the tendency to equilibrium may reassert 
itself in the minor characteristics, and they may, as it were, 
crystallise once more in a form not dissimilar in generic 
type. If among a certain assemblage of individuals con- 
stituting a species, the tendency to maintain the specific 
equilibrium be (as it should be a priori) transmitted to the 
progeny in different degrees of intensity, a gradual separa- 
tion might take place between those with a _ stronger 
tendency to equilibrium and those with less. Here natural 
selection would come in. Those yielding as above to the 
pressure of the environment would necessarily become better 
adapted to it (or perish) and with their changed generic 
structure might be able to persist. On the other hand, those 


— 


spine sit SOE 


332 DARWINISM TO-DAY, 


with the broader base, so to speak, with the inherited 
tendency to remain unshaken by the modifications of the 
environment, may be conceived as through this tendency 
to be and to remain less injuriously affected by adverse 
circumstances, and consequently might still endure. In 
short, natural selection in the one case would find its ful- 
crum in the tendency to easy adjustment of characters ; and 
in the other case in the inherited persistency in equilibrium 
rendering its possessor more or less indifferent to the in- 
jurious elements of the environment. The intermediate 
individuals by the hypothesis would be those least-fitted to 
persist in any case and hence liable to be rapidly eliminated. 
Then we should have parallel series of species in two or even 
more genera existing simultaneously.” 

Francis Galton, the great student of heredity and, in most 
of his belief a thorough Darwinian, nevertheless held it to be 

probable that evolution might proceed not only 
_ Galton’s belief Hy minute steps but that decisive sudden changes 
in discontinuous ‘ 
steps. of the type may occur. “That the steps may 
be small and that they must be small are very 

different views; it is only to the latter that I object, and 
only when the indefinite word ‘small’ is used in the sense of 
‘barely discernible’ or as small compared with such large 
sports as are known to have been the origin of new races.” * 
And his familiar analogy of organic stability to that of the 
polygon” with unequal sides, whose stability or fixity de- 
pends upon which of these sides it may be resting on, ex- 
presses well the basic idea in heterogenesis or mutation by 
small but definitive and fairly stable changes. Galton also 
believed in the stability or fixity of sports; not that all trans- 
mit their character to their young but that many do and thus 
give rise to new types. 

Emery,’ in his suggestive paper called “Gedanken zur 
Descendenz- und Vererbungstheorie,’ expresses his belief 
in the importance in species-forming of what he calls “pri- 


OTHER SIHEORIES OF SPECIES-EFORMING, 333 


b 


mary variations,’ which are large and sudden as contrasted 
with “secondary variations,’ which are the usual small, 
Saeteie fluctuating or so-called Darwinian variations. 
ory of ‘primary emery bases his belief on the few cases like 
variations.” the. Ancon sheep and the inherited six-fingered- 
ness of men, and also on an argument drawn from the dif- 
ficulty of explaining by the natural selection theory various 
existing conditions such as sexual polymorphism, and numer- 
ous cases of extremely complex structural and physiological 
specialisation. But there is little that is convincing in 
Emery’s presentation. 

A later exponent of heterogenesis of a different kind, and 
a more sharply-spoken antagonist of the selection theory, 

KGreahinak y's much more nearly anticipates de Vries’s muta | 
theory of hetero- tion theory. Indeed this biologist, the Russian 
lg botanist Korschinsky, in his championship of 
heterogenesis goes much beyond de Vries in his denial of the 
influence of selection in species-forming and descent. De 
Vries, as we shall see, admits natural selection to be a factor, 
and perhaps a large one in the determination of descent, of 
organic evolution, but holds it to be wholly a restraining and 
cutting-back factor, not at all a formative one. Korschinsky 
says plainly that the struggle for existence and selection 
have either no influence in species-forming and descent, or, 
if any, a hindering and antagonising influence, a retarding 
and nullifying influence. Korschinsky has published his 
theory in three papers, one a large work in Russian which I 
have not seen, the others shorter papers ** in German which 
are of the nature of vorlaiifige Mitteilungen. In these 
papers he formulates clearly and positively a theory of 
heterogenesis or species-forming by “mutations” and attacks 
sharply and positively the natural selection theory. A con- 
cise statement of his theory and at the same time of his 
position with regard to the selection theory is given by 
him in a table of two columns in which the contrast between 


50+ 


the two theories is graphically shown. 


DARWINISM TO-DAY. 


I translate here this 


“parallel columns” statement in full: 


ACCORDING TO THE TRANSMUTA- 
TION THEORY. 


1. To all organisms there be- 
longs a capacity for variation 
which is called into play partly 
through inner, partly through 
outer causes, through use and 
disuse, etc. This capacity for 
variation regularly finds its ex- 
pression in the appearance of 
slight and unnoticeable individ- 
ual differences. 

2. As a result of this strug- 
gle for existence and selection, 
those individual variations 
which prove themselves useful 
become fixed and accumulated, 
while the non-useful ones dis- 
appear. All characteristics and 
peculiarities of a species must, 
as a result of a prolonged selec- 
tion, stand in harmony with the 
outer conditions, and be useful 
to the organism. 

3. Through prolonged selec- 
tion and accumulation of char- 
acteristics all species undergo 
a persistent change, whereby 
they are gradually transformed 
into new species without, how- 
ever, sacrificing their normal 
physiological relations. 


4. This process can take place 
everywhere and under all cir- 
cumstances. The harder the 
outer conditions and the sharp- 
er the struggle for existence, 
the more energetically selection 
works, and therewith the quick- 


ACCORDING TO THE THEORY OF 
HETEROGENESIS. 


1. To all organisms there be- 
longs a capacity for variation, 
which is a fundamental inner 
peculiarity independent of outer 
conditions, and which remains 
usually in latent condition, re- 
tained by heredity, but which 
now and then finds its expres- 
sion in sudden changes. 


2. These sudden changes can, 
under favourable conditions, be 
the beginnings of persistent 
races. These new characteris- 
tics, having appeared independ- 
ently of outer conditions, are 
sometimes useful to the organ- 
ism, but they may also stand in 
no harmony with outer condi- 
tions. 


_ 3. All once-formed species re- 
main unchanged, although new 
forms occasionally split off from 
them by heterogenesis. Such 
newly-arisen forms have, as the 
result of a disturbed heredity, a 
deranged constitution, which re- 
veals itself in a lessened fertility 
and often in a generally weak- 
ened condition of the organism. 
The new forms, becoming con- 
stant races, gradually recover 
their constitution. 

4. The origin of new forms 
can, however, occur only under 
favourable conditions of exist- 
ence for the species, and the 
more favourable these condi- 
tions, that is, the less severe 
the struggle for existence, the 


OTHER THEORIES OF SPECIES-FORMING. 


er the development of new 


forms. 


5. The chief requisite for evo- 
lution is, therefore, the struggle 
for existence and the selection 
which results from it. 


6. If there were no struggle 
for existence, no selection, no 
survival of the strongest, there 
would be no evolution and no 
specialisation, for adapted spe- 
cies would have no advantage 
over unadapted ones, and as a 
result of crossing with the lat- 
ter, they would sacrifice their 
useful characteristics. 


7. The so-called advance in 
nature or the perfecting of or- 
ganisms, is nothing else than a 
more complex, more complete 
adaptation to outer conditions, 
and it is reached in a purely 
mechanical way through selec- 
tion and the accumulation of 
characteristics useful under the 
existent outer conditions. 


335 


more energetically can evolution 
go on. New forms do not arise 
under hard external conditions, 
or if any do, they go quickly to 
ground. 

5. The struggle for existence, 
and the selection that goes hand 
in hand with it, constitute a fac- 
tor which limits new forms and 
hinders further variation and is, 
therefore, in no way favourable 
to the origin of new forms. It 
is a factor inimical to evolution. 

6. If there were no struggle 
for existence, there would be no 
killing out of newly arising or al- 
ready arisen forms. The world 
of organisms could then grow to 
a mighty tree, whose branches. 
could all persist in blossoming 
condition, and the most aberrant, 
now isolated, species would be 
connected with all others through 


intermediate forms. 

7 ou hes adaptation woe h 
comes to exist through the 
struggle for existence is not at 
all identical with an advance, for 
higher, more specialised (voll- 
kommenere) forms are by no 
means alwavs better adapted to 
outer conditions than the lower 
ones. One cannot explain the 
evolution of organisms in a 
purely mechanical way. In or- 
der to explain the origin of 
higher forms out of lower it is 
necessary to admit a_ special 
tendency, in organisms, for ad- 
vance, which is nearly related 
to, or identical with the tend- 
ency to vary, and which com- 
pels organisms toward perfect- 
ness as far as external conditions 
allow. 


The theory of heterogenesis as formulated by Korschinsky 
(and also as held by de Vries, as we shall see) is not neces- 


336 DARWINISM TO-DAY. 


sarily a theory of sudden large changes or variations, al- 
though it is of sudden and fixed ones. It is not based on 
any belief that sports or large variations are any more 
numerous, nor of any more worth as the beginnings of new 
species, than now generally recognised, but it assumes 
sudden radical changes in the organism which, if not visibly 
large as regards obvious quantitative conditions, are large or 
at least comprehensive as regards qualitative conditions. 
The mutation or variation assumed by the theory of hetero- | 
genesis affects many organs and parts, structurally and 
physiologically ; it produces a radical change throughout the 
organism. And this change is the result of an influence 
wholly intrinsic, inherent, and has no reference to external 
conditions, except in that the stimulus for it may come partly 
or chiefly from specially favourable conditions of nutrition. 
This change is at once definitive and fixed: it is transmitted 
unimpaired to the offspring of the organism showing the 
mutation, only the capacity for the production of offspring, 
1. €., the reproductive fertility, is often weakened. 

Korschinsky’s theory and declarations are not based on 
any very large amount of personal experimentation and 
observation—at least his references to new facts are few and 
meagre. He gives a short list of old and more or less 
familiar together with a few new examples of heterogenesis 
but he does not lend the theory of heterogenesis very much 
in the way of authority, except in so far as the evidently 
positive and clear conviction on the part of a biologist of 
experience and reputable standing of the necessity and truth 
of such a theory is authority. Korschinsky’s conviction is 
probably based on much observation and experience besides 
that which he definitely catalogued, but what is needed to 
carry conviction to others is direct reference to proved, and 
where possible verifiable, facts of observation and experi- 
ment. 

The supplying of this demand, to a degree which will 


OTHER THEORIES OF SPECIES-FORMING. 337 


appear to various people insufficient or sufficient according 
to their respective ideas of what is needed in 

De Vriesand the way Of fact material for the satisfactory 
pears founding of a theory, it is the special vir- 

tue of de Vries to have attempted on behalf 
of heterogenesis. 

De Vries ** introduces his now classic two-volume pres- 
entation of his views’on evolution and species-forming 
(“Die Mutationstheorie,” 1901-1903) with the following 
paragraph: 

“Als Mutationstheorie bezeichne ich den Satz, dass die 
Eigenschaften der Organismen aus scharf von einander 
unterschiedenen Einheiten aufgebaut sind. Diese Einheiten 
konnen zu Gruppen verbunden sein, und in verwandten 
Arten kehren dieselben Einheiten tnd Gruppen wieder. 
Ubergange, wie sie uns die ausseren Formen der Pflanzen 
und Thiere so zahlreich darbieten, giebt es aber zwischen 
diesen Einheiten ebensowenig, wie zwischen den Molektlen 
der Chemie.” And again in the first paragraph of the 
preface to his book “Species and Varieties” ** (an edited 
transcription of his American lectures on species-forming, 
delivered in California in 1904) he says: “. . . but the , 
way in which one species originates from another has not | 
been adequately explained. The current belief assumes that | 
species are slowly changed into new types. In contradic- 
tion to this conception the theory of mutation assumes that 
new species and varieties are produced from existing forms 
by sudden leaps. The parent-type itself remains unchanged 
throughout this process, and may repeatedly give birth to 
new forms. These may arise simultaneously and in groups, 
or separately at more or less widely distributed periods.” 

Obviously there is no ambiguity here as to the relation 
of species-forming by mutation to species-forming by 
gradual modification through selection or fluctuating varia- 
tions. In the words of de Vries: “Species have not arisen 


338 DARWINISM TO-DAY. 


through gradual selection continued for hundreds -or thou- 
sands of years, but by jumps (stufenweise) through sudden, 
though small, transformations. In contrast with variations 
which are changes in a linear direction the transformations 
to be called mutations constitute divergence in new directions. 
They take place, so far as experience goes, without definite 
direction.” ** And even if transition forms exist between 
the species produced by mutations, they are no evidence 
against the mutations, “‘for,’”’ says de Vries, “the transitions 
do not appear before the new species, at most only simul- 
taneously with this, and generally only after this is already 
in existence. The transitions are therefore no intermediates 
or preparations for the appearance of the new forms. The 
origin takes place, not through them, but wholly independ- 
ently of them.” ” | | 
Too often de Vries’s theory is said not to be alternative 
with Darwin’s, but auxiliary to it. As regards the forma- 
tion of new species, the two theories are directly 
De Vries’s in opposition. But as regards the general 
aie course of organic evolution (which is another 


opposition to 
Darwin's as con- matter) the mutations theory is not in contra- 


SNE diction to the theory of descent through 

selection. De Vries himself says: “Notwith- 
standing all these apparently unsurmountable difficulties, 
Darwin discovered the great principle which rules the evolu- 
tion of organisms. It is the principle of natural selection. 
It is the sifting out of all organisms of minor worth through 
the struggle for life. It is only a sieve, and not a force of 
nature, no direct cause of improvement, as many of Dar- 
_ win’s adversaries, and unfortunately many of his followers 
also, have so often asserted. It is only a sieve, which de- 
cides which is to live, and what is to die. But evolutionary 
lines are of great length, and the evolution of a flower or 
of an insectivorous plant is a way with many side-paths. It 
is the sieve that keeps evolution on the main line, killing 


~ 


OTHER THEORIES OF SPECIES-FORMING, SM 


all or nearly all that try to go in other directions. By this 
means natural selection is the one directing cause of the 
broad lines of evolution.” ** 

While de Vries admits that recorded mutations are few; 
“mutations under observation are as yet very rare; enough 
to indicate the possible and most probable ways but no 
more;” *’ yet he strongly maintains that there is no scientific 
proof of the origin of species in any other way than by 
mutation and that there is such proof of their actual muta- 
tional origin. He says: “I intend to give a review of the 
facts obtained from plants which go to prove the assertion 
that species and varieties have originated by mutation and 
are, at present, not known to originate in another way.” 

But in any consideration of de Vries’s work and theories, 
one must have clearly in mind the distinctive meaning 
which de Vries attaches to the word species. However 
little biologists agree on any absolute definition of species, 
the term nevertheless is consistently used to refer to differ- 
entiated organic types between any two of which there is 
considerable obvious describable difference, either quali- 
tative or quantitative. If two types of such obvious differ- 
ence in one or several characteristics (usually external or 
at least externally noticeable differences are the ones used) 
are connected by a series of connecting gradatory forms 
existing either in the same territory or in other regions, the 
two forms are not referred to as distinct species but as 
varieties ; at least the form at one end of the series is called 
a variety of the form at the other end. But de Vries’s 
species and varieties are of different stuff. Specific dis- 
tinctions with him are based on differences in aggregation 
of the elementary units, the Einheiten, that go to compose 
the specific types. “Species is a word,’ says de Vries, 
“which always has had a double meaning. One of them is 
the systematic species, which is the unit of our system. 
But these units are not at all indivisible. Long ago Lin- 


340 DARWINISM TO-DAY. 


nzeus knew them to be compound ideas in a great number 
of instances, and increasing knowledge has shown that the 
same rule prevails in other instances. To-day the vast ma- 
jority of the old systematic species are known to consist of 
minor units. These minor entities are called varieties in sys- 
tematic works. However, there are many objections to this 
usage. First, the term variety is applied in horticulture and 
agriculture to things so widely divergent as to convey no 
clear idea at all. Secondly, the subdivisions of species are 
by no means all of the same nature, and the systematic 
varieties include units the real value of which is widely 
different in different cases. Some of these varieties are in 
reality as good as species, and have been ‘elevated,’ as it is 
called, by some writers, to this rank. This conception of the 
elementary species would be quite justifiable, and would at 
once get rid of all difficulties, were it not for one practical 
obstacle. The number of the species in all genera would be 
doubled and tripled, and as these numbers are already 
cumbersome in many cases, the distinction of the native 
species of any given country would lose most of its charm 
and interest. 

“In order to meet this difficulty we must recognise two 
sorts of species. The systematic species are the practical 
units of the systematists and florists, and all friends of wild 
nature should do their utmost to preserve them as Linnzus 
has proposed them. These units, however, are not really 
existing entities; they have as little claim to be regarded 
as such as the genera and families have. The real units 
are the elementary species; their limits often apparently 
overlap and can only in rare cases be determined on the 
sole ground of field-observations. Pedigree-culture is the 
method required and any form which remains constant and 
distinct from its allies in the garden is to be considered as 
an elementary species.” *” 

With regard to varieties de Vries has the following to 


OTHER THEORIES OF SPECIFS-FORMING. 341 


say: “Linnzus himself knew that in some cases all sub- 
divisions of a species are of equal rank, together constituting 
the group called species. No one of them outranks the 
others; it is not a species with varieties, but a group con- 
sisting only of varieties. A closer inquiry into the cases 
treated in this manner by the great master of systematic 
science shows that here his varieties were exactly what we 
now call’elementary species. 

“In other cases the varieties are of a derivative nature. 
The species constitutes a type that is pure in a race which 
ordinarily is still growing somewhere, though in some cases 
it may have died out. From this type the varieties are 
derived, and the way of this derivation is usually quite 
manifest to the botanist. It is ordinarily by the disappear- 
ance of some superficial character that a variety is dis- 
tinguished from its species, as by the lack of colour in the 
flowers, of hairs on stems and foliage, of the spines and 
thorns, etc. Such varieties are, strictly speaking, not to be 
treated in the same way as elementary species, though they 
often are. We shall designate them by the term of ‘retro- 
grade varieties, which clearly indicates the nature of their 
relationship to the species from which they are assumed to | 
have sprung. In order to lay more stress on the contrast | 
between elementary species and retrograde varieties, it) 
should be stated at once, that the first are considered to, 
have originated from their parent-form in a progressive 
way. They have succeeded in attaining something quite 
new for themselves, while retrograde varieties have only 
thrown off some peculiarity, previously acquired by their 
ancestors.” *” 

With regard to the facts and general evidence *’ on which 

ee: de Vries bases his beliefs and theory a few 
basis of de words, too few, I regret, must suffice. Like 
Vries's theory. Darwin, de Vries only came to the full pub- 
lication of his theory after many years of assiduous obser- 


a 


342 DARWINISM TO-DAY. 


vation, of persistent compilation of other men’s observing, 
and careful weighing and consideration of the data in 
hand. In de Vries’s case too there was added a large 
amount of experimental testing of his conclusions. This 
experimental study of the species-forming problem de 
Vries and his followers rather seem to claim as a distinct- 
ively new part of the basis for the mutations theory, but as 
a matter of fact Darwin himself, in much less degree per- 
haps, and in somewhat different manner, appealed to experi- 
ment to test many of his conclusions. The actual forming 
of new species by selection could not be experimentally 
tested or proven by Darwin. Whether biologists are ready 
to accept de Vries’s pedigree-culture work and results as 
of the same nature of rigid experimental test and proof as 
there exists in experimentation in chemistry and static 
physics (for that is the claim for the new “experimental 
method” in biology) remains, perhaps, a moot point. De 
Vries’s general statement of the character and the amount 
of the evidence on which he rests his belief in the formation 
of species by mutation is contained in the following para- 
graphs from his book “Species and Varieties’ (p. 22). 
“Mutations are occurring from time to time in the wild 
state as well as in horticulture and agriculture. A selec- 


tion of the most interesting instances will be given later. 


But in all such cases the experimental proof is wanting. 
The observations, as a rule, only began when the mutation 
made its appearance. A more or less vague remembrance 
about the previous state of the plants in question might be 
available, though even this is generally absent. But. on 
doubtful points concerning possible crosses or possible intro- 
duction of foreign strains, mere recollection is insufficient. 
The fact of the mutation may be very probable, but the full 
proof is, of course, wanting. Such is the case with the 
mutative origin of Xanthium commune Wootom from New 
Mexico and of Cnothera biennis cruciata from Holland. 


OTHER THEORIES OF. SPECIES-FORMING. | 343 


The same doubt exists as to the origin of the Capsella 
Heegert of Solms-Laubach, and of the oldest recorded muta- 
tion, that of Chelidonium lacimiatum in Heidelberg about 
1600.” 

Next, after introducing the necessity of experimental 
proof and explaining how one must go to work to acquire 
such proof he refers to his own well-known work with 
Lamarck’s evening primrose as follows (pp. 26-29) : 

“Complying with these conditions, the origin of species 
may be seen as easily as any other phenomenon. It is only 

necessary to have a plant in a mutable condi- 

The work with tion. Not all species are in such a state at 
Lamarck’s even- 
ing primrose, Present, and therefore I have begun by ascer- 

taining which were stable and which were not. 
These attempts, of course, had to be made in the experi- 
mental garden, and large quantities of seed had to be pro- 
cured and sown. Cultivated plants, of course, had only a 
small chance to exhibit new qualities, as they have been so 
strictly controlled during so many years. Moreover their 
purity of origin is in many cases doubtful. Among the wild 
plants only those could be expected to reward the investi- 
gator which were of easy cultivation. For this reason I 
have limited myself to the trial of wild plants of Holland, 
and have had the good fortune to find among them at least 
one species in a state of mutability. It was not really a 
native plant, but one probably introduced from America 
or at least belonging to an American genus. It was the 
great evening-primrose or the primrose of Lamarck. A 
strain of this beautiful species is growing on an abandoned 
field in the vicinity of Hilversum, at a short distance from 
Amsterdam. Here it has escaped from a park, and multi- 
plied. In doing so it has produced, and is still producing, 
quite a number of new types, some of which may be con- 
sidered as retrograde varieties, while others evidently are 
of the nature of progressive elementary species. 


344 DARWINISM TO-DAY, 


“This interesting plant has afforded me the means of ob- 
serving directly how new species originate, and of studying 
the laws of these changes. My researches have followed a 
double line of inquiry. On one side, I have limited myself 
to direct field observations, and to trials of seed, collected 
from the wild plants in their native locality. Obviously the 
mutations are decided within the seed, and the culture of 
young plants from them had no other aim than that of 
ascertaining what had occurred in the field. But then the 
many chances of destruction that threaten young plants in a 
wild state could be avoided in the garden, where environ- 
mental factors can be controlled. 

“My second line of inquiry was an experimental repetition 
of the phenomena which were only partly discerned at the 
native locality. It was not my aim to intrude into the 
process, nor to try to bring out new features. My only ob- 
ject was to submit to the precepts just given concerning 
pure treatment, individual seed-gathering, exclusion of 
crosses, and accurate recording of all the facts. The result 
has been a pedigree which now permits of stating the rela- 
tion between all the descendants of my original introduced 
plant. This pedigree at once exhibits the laws followed by 
the mutating species. The main fact is, that it does not 
change itself gradually, but remains unaffected during all 
succeeding generations. It only throws off new forms, 
which are sharply contrasted with the parent, and which 
are from the very beginning as perfect and as constant, as 
narrowly defined, and as pure of type as might be expected 
of any species. 

“These new species are not produced once or in single 
individuals, but yearly and in large numbers. The whole 
phenomenon conveys the idea of a close group of mutations, 
all belonging to one single condition of mutability. Of 
course this mutable state must have had a beginning, as it 
must sometime come to an end. It is to be considered as a 


OTHER THEORIES OF -SPECIES-FORMING, 345 


period within the life-time of the species, and probably it is 
only a small part of it.” 

The following paragraphs and diagram quoted from 
Morgan ** give an admirably concise statement of the actual 
details of the primrose mutations observed by de Vries. 

“We may now proceed to examine the evidence from 
which de Vries has been led to the general conclusions given 

in the preceding pages. De Vries found at 
Morgan’s : ‘ 
account ofde  Liilversum, near Amsterdam, a locality where 
Lab experl- g number of plants of the evening primrose, 
j CEnothera lamarckiana, grow in large numbers. 
This plant is an American form [native to the Southern 
United States] that has been imported into Europe. It 
often escapes from cultivation, as is the case at Hilversum, 
where for ten years it has been growing wild. Its rapid 
increase in numbers in the course of a few years may be one 
of the causes that have led to the appearance of a mutation 
period. The escaped plants showed fluctuating variations 
in nearly all of their organs. They also had produced a 
number of abnormal forms. Some of the plants came to 
maturity in one year, others in two, or in rare cases in 
three, years. 

“A year after the first finding of these plants de Vries 
observed two well-characterised forms, which he at once 
recognised as new elementary species. One of these was 
O. brevistylis, which occurred only as female plants. The 
other new species was a smooth-leafed form with a more 
beautiful foliage than O. lamarckiana. This is O. levifolia. 
It was found that both of these new forms bred true from 
self-fertilised seeds. At first only a few specimens were 
found, each form in a particular part of the field, which 
looks as though each might have come from the seeds of a 
single plant. | 

“These two new forms, as well as the common O. la- 
marckiana, were collected, and from these plants there have 


346 DARWINISM TO-DAY. 


arisen the three groups or families of elementary species that 
de Vries has studied. In his garden other new forms also 
arose from those that had been brought under cultivation. 
The largest group and the most important one is that from 
the original O. lamarckiana form. The accompanying table 


CGENOTHERA LAMARCKIANA. 


ELEMENTARY SPECIES, 

















3 % 1 4 * 7. = 
GENERATION. nal og ee Pea Bg a : 3p 
m| 2 | afer) 8s | 84 2 le 
CR ee baton 4 ZN ed iy 
Ved T Line Stee eteas 8 Gener. 5 I Olena) 700 ue2r I 
1899 = ——~+,- erate 
annual 
NAS Ute terres 7 Gener. 9 OF s63 GOO matt 
1898 Sn ete 
annual 
Ah Care smeeacunte ma 6 Gener. Tigo 3. st 8000 EO 5 I 
1897 a cr 
annual 
Witereien’. cae es 5 Gener. 25° "135. 20) 18,000 “49 14z7up 
1896 nes poe a 
annual 
Nigro ach cs cts 4 Gener. tl a tte FG Le. 8. 34;000) "60.473 I 
1895 OF 
annual 
DE worse eae 3 Gener. I} 10,0007604 3 
1890-91 ET 
biennial 
oe coos 4 2 Gener. 15-000) 7055 5 
1888-89 Rak Spee a, 
biennial 
Le a artioes 1 Gener. 9 
1886-87 
biennial 


shows the mutations that arose between 1887 and 1899 from 
these plants. The seeds were selected in each case from 
self-fertilised plants of the /Jamarckiana form, so that the 
new plants appearing in each horizontal line are the 
descendants in each generation of /amarckiana parents. It 
will be observed that the species, O. oblongata, appeared 
again and again in considerable numbers, and the same is 


OTHER: THEORIES OF: SPECIES-FORMING. 347 


true for several of the other forms also. Only the two 
species, O. gigas and QO. scintillans, appeared very rarely. 


“Thus de Vries had, in his seven generations, about fifty // 


thousand plants, and about eight hundred of these were i 
mutations. When the flowers of the new forms were arti- 
ficially fertilised with pollen from the flowers on the same | 
plant, or of the same kind of plant, they gave rise to forms | 
like themselves, thus showing that they are true elementary | 
species.* It is also a point of some interest to observe that 
all these forms differed from each other in a large number 
of particulars. 

“Only one form, O. scintillans, that appeared eight times, 
is not constant as are the other species. When self- 
fertilised its seeds produce always three other forms, O. 
scintillans, O. oblongata, and O. lamarckiana. It differs in 
this respect from all the other elementary species, which 
mutate not more than once in ten thousand individuals. 

“From the seeds of one of the new forms, O. levifolia, col- 
lected in the field, plants were reared, some of which were 
O. lamarckiana and others O, levifolia. They were allowed 
to grow together, and their descendants gave rise to the 
same forms found in the Jamarckiana family, described 
above, namely, O. Jata, elliptica, nannella, rubrinervis, and 
also two new species, O. spatulata and leptocarpa. 

“In the Jata family only female flowers are produced, and, 
therefore, in order to obtain seeds they were fertilised with 
pollen from other species. Here also appeared some of the 
new species already mentioned, namely, albida, nannella, 
lata, oblongata, rubrinervis, and also two new species, ellip- 
tica and subovata. 

“De Vries also watched the field from which the original 
forms were obtained, and found there many of the new 
species that appeared under cultivation. These were found, 


* O. lata is always female, and cannot, therefore, be self-fertilised. 
When crossed with O. lamarckiana there is produced fifteen to twenty 
per cent. of pure /Jata individuals. 


348 DARWINISM TO-DAY. 


however, only as weak young plants that rarely flowered. 
Five of the new forms were seen either in the Hilversum 
field; or else raised from seeds that had been collected there. 
These facts show that the new species are not due to culti- 


|, vation, and that they arise year after year from the seeds 


' of the parent form, O. lamarckiana.” 


RN 


Since the publication of de Vries’s theory and the data’ 
and considerations on which it is based (these considera- 
. tions including an unusually keen and effective 
Laine! criticism of the Darwinian factors of species- 
ward the muta- forming) a great deal of discussion of the 
tions theory. E P 
theory has been indulged in. On the whole 
the theory has been warmly welcomed as the most promis- 
ing way yet presented ** out of the difficulties into which 
biologists had fallen in their attempts.to explain satisfactorily 
the phenomena of the origin of species through Darwinian 
selection. And especially has been welcomed the fruitful idea 
of unit species characters, and of the indivisibility and the 
distinctness of such characters in inheritance. But with all 
the interest aroused by de Vries’s presentation of his theory, 
and with all the eager scrutiny of species and records of 
species-appearing an output of new evidence amazingly 
small (when one stops to consider the publicity gained for 
the theory itself and its obvious need of more confirmatory 
data of observation and experiment) has resulted. Even 
though the answer may be that experiment takes time, the 
lack of new observational evidence of the occurrence of 
mutations,’ and of the origin of new species through muta- 
tions in nature, is significant. It is my belief that a reaction 
against the curiously swift and widespread partial to com- 
plete acceptance of the mutation theory as the sufficient “way 
out” of our troubles to explain the origin of new species will 
soon occur. (See notes 24, 25, and 26, the appendix of this 
chapter, for references to certain recent criticisms of the 
mutation theory. ) 


OTHER THEORIES OF SPECIES-FORMING. 349 


In closing this confessedly inadequate consideration of 
the important work and theorising of de Vries we should 
not fail to note that the mutations theory 1s 


Mutations : t me Hecho 41 F a 
theory. con- in strong contrast to any theory of species- 
trasted with forming based on Lamarckian principles in that 
Lamarckism, 


the newly appearing differences in organisms 
leading to the establishment of new species are purely con- 
genital: that is, the mutations arise in one or both of the 
sex cells and only later appear in the adult organism. There. 
is no question of the transference to the germ-cells of 
changes induced in the soma by use or disuse or functional 
stimulus in such a way as to result in the photographic 
reappearance of these changes in the offspring. Mutations 
are true congenital or blastogenic variations. “The muta- | 
tion theory,” well says Conklin,*’ “is a theory of the evolu- 
tion of organisms through the evolution of their germ-cells.” 

The mutations theory is also in sharp contrast to the 
theory of species-forming by geographical isolation (see 

chapter ix). According to de Vries many dis- 

Mutations : . eet é 

theory contrasted tinct species (de Vriesian elementary species) 
Heese can and do exist side by side in the same range. 

In fact they “are found to be heaped up in the 
centre of their area of distribution, but are more scattered 
at the periphery.” ** Now according to Wagner, Gulick, 
and Jordan two closely allied species, 7. e., stock and off- 
shoot, are found practically never to inhabit the same range, 
except in those cases where a migration of one type into 
the territory of the other has taken place after the differ- 
entiation has been effected (by previous segregation). 

It would carry us into too extended a discussion to at- 
tempt to sum up here the pertinent criticism that has been 
directed against the mutations theory. As already indicated, 
there is plenty of it and of distinctly non-negligible char- 
acter. But just now it seems to me sufficient simply to call 
attention to the extreme meagreness in quantity of the real 


350 DARWINISM TO-DAY. 


scientific evidence for the theory as a theory capable of ex- 
plaining species-forming as a whole. There is probably no 
gainsaying the actuality of the occurrence of certain muta- 
tions (in de Vries’s sense) nor of their establishment of 
certain apparently fixed new organic types (de Vries’s 
elementary species of Cénothera). But this is very far 
from accepting the mutations theory as a sufficient causal 
explanation of the origin of the hundreds of thousands of 
species of animals and plants that are now or were formerly 
existent. 

As for the help that the establishment of the mutations 
theory would give those biologists who reject the natural 

Moreen cane selection theory of species-forming, Morgan * 
mation ofthe writes as follows, summing up the advantages 
advantages of 
ae aria ume O betes ticatr: 
theory, “1. Since the mutations appear fully formed 
from the beginning, there is no difficulty in accounting for 
the incipient stages in the development of an organ, and 
since the organ may persist, even when it has no value to 
the race, it may become further developed by later muta- 
tions and may come to have finally an important relation to 
the life of the individual. . 

“2. The new mutations may appear in large numbers, and 
of the different kinds those. will persist that can get a: foot- 
hold. On account of the large number of times that the 
same mutations appear, the danger of becoming swamped 
through crossing with the original form will be lessened 
in proportion to the number of new individuals that arise. 

“3, If the time of reaching maturity in the new form is 
different from that in the parent forms, then the new species 
will be kept from crossing with the parent form, and since 
this new character will be present from the beginning, the 
new form will have much better chances of surviving than 
if a difference in time of reaching maturity had to be gradu- 
ally acquired. 


OTHER THEORIES OF SPECIES-FORMING. 351r 


“4. The new species that appear may be in some cases. 
already adapted to live in a different environment from that 
occupied by the parent form; and if so, it will be isolated 
from the beginning, which will be an advantage in avoiding 
the bad effects of intercrossing. 

“s. It is well known that the differences between related 
species consist largely in differences of unimportant organs, 
and this is in harmony with the mutation theory, but one 
of the real difficulties of the selection theory. 

“6. Useless or even slightly injurious characters may 
appear as mutations, and if they do not seriously affect the 
perpetuation of the race, they may persist.” 

Finally, the attention of students especially may be called 
to Bateson’s interesting suggestion that mutations may be 

Shonen ries simply pure Mendelian recessives appearing 
gestion thatmu- after a crossing. It would take us too far 
tations are 5 
Mendelian ro. ~auield to attempt to explain here to readers 
cessives. unacquainted with the Mendelian principles 
of inheritance just how Bateson’s suggestion has a certain 
plausibility. It must suffice to say that Mendel, and after 
him a considerable number of present-day students of 
heredity, have shown that after a crossing between two. 
individuals sharply contrasting in regard to some particular 
character, as colour of hair, all the offspring of the first 
generation may agree in showing but one of the two parental 
colours (the dominant), but that if these first generation 
offspring are bred to each other, or to similarly produced in-. 
dividuals, the members of the second generation will split 
up as regards the character in question, some showing one 
of the grand-parental hair colours, and the rest showing the 
other one. Now breeding likes together, it would be shown 
in third generation groups that one of these colours, and,. 
namely, that one called the recessive, which did not appear 
at all in the first generation, will always henceforth breed 
true while the other colour may or may not breed true (de-. 


352 DARWINISM TO-DAY. 


pending on whether in making the matings pure dominants 
or cross-bred dominants happen to be used). Thus the 
sudden appearance in the second generation of the latent or 
recessive characteristic, and its breeding true, are occur- 
rences which might readily be interpreted as the appearance 
of a mutation or true-breeding sport by an observer unac- 
quainted with the ancestry of the individuals under his eye. 

Alternative Theories to Explain Secondary Sexual Char- 
acters.—Before closing this discussion of theories which 
have been proposed as substitutes for the Darwinian selec- 
tion theories to explain the actual conditions in the organic 
world as we see it to-day, and as we know it to have been 
in past ages, we should mention, at least, the few attempts 
to formulate a substitute explanation for the existence of 
secondary sexual characters. The discrediting of the sexual 
selection theory as such an explanation is certainly nearly 
complete. But it is interesting to note how lame and uncon- 
vincing are the proposed substitute explanations. 

The first, and most appealing one, is the explanation that 
the extra plumes, wattles, horns, the unusual display of 

bright colours, etc., of the males are simply the 

Extra growths manifestations of an extra growth-force or 
the result of ‘ be : F 
extravigour, Vigour exhibited by the male in the breeding 

season. The female also may be endowed with 
extra growth-vigour at this time, but it goes, in her case, to 
the formation of ova, to the storing up of food in or around 
the egg cells. The songs, the dances, the violent play and 
antics of the males common to many species of birds, insects, 
spiders, etc., are also attributed to this special or sexual 
vigour. 

Now while such secondary sexual characters as colour, 
plumes, wattles, etc., might perhaps well enough seem to 
be the outcome of an extra growth-vigour, what about such 
special male characters as the stridulating organs of male 
katydids and crickets, and other similar complex, highly 


OTHER THEORIES OF SPECIES-FORMING. $55 


perfected, adaptive structures? A male cricket has the 
veins at the base of one wing-cover curiously and com- 
plexly modified in course and in superficial structure, while 
the veins of the other wing-cover are also modified in a way 
differing from but exactly correlated with the venation of 
the first wing, the whole specialisation resulting in a com- 
bination of file, scraper, and vibrating membrane to form the 
effective musical instrument of the insect. Can such an 
adaptive structural modification be conceived to be a sudden 
bursting forth or result of superabundant growth-force? 
And many of the secondary sexual characters are of this 
class of complex adaptive specialisations. The growth- 
force explanation can, at best, explain but few of the various 
categories of sexual dimorphism. Some explanation more 
directive in its character is needed for these others. 
Even more restricted in its application, and less con- 
vincing in the assumptions at its very base, is the curious 
replacement theory of Emery.*’ This investi- 
Emery’s theory ; : ; 
of the origin of gator believes that sexual selection can explain 
secondary sexual but few if any cases of sexual dimorphism, and 
characters, : 
would explain these other cases largely by the 
sudden appearance (mutation or sport) of a second form 
of male or female, the persistence for a while of the two 
forms side by side, as now exemplified by numerous dimor- 
phic or polymorphic (or di- or polychromatic) species, and 
then the gradual or sudden dying out (killing out by selec- 
tion?) of the older original form (the one resembling the 
other sex), thus leaving the once dimorphic sex represented 
only by the newer aberrant form. While such an explana- 
tion may possibly explain a few cases of extreme sexual 
dimorphism or dichromatism, it certainly will not do for 
the many cases of secondary sexual difference constituted 
by the existence in one sex of some one or few particular 
adaptive specialisations for music-making, scent-producing, 
or weapon-forming, not possessed by the other sex. 


354 DARWINISM TO-DAY. 


Cunningham *’ (and also at about the same time Wigles- 
worth) in 1898 suggested, on a neo-Lamarckian basis, that 
secondary sexual characters were due to the 
caaanel stimulation of parts through use or external - 
secondary sexual yjolence or irritation. Cunningham would ex- 
characters, : : ; rat: 
plain all adaptations as derived from variations 
actually induced by responses or reactions to the environ- 
ment. His theory of the origin of secondary sexual char- 
acters would simply be the explanation of the adaptive dif- 
ferences between two individuals of a species on the same 
basis as the explanation of the adaptive differences between 
individuals of different species. His argument is summed 
up as follows: “Selection assumes the occurrence of varia- 
tions; the variations must either be similarly indefinite and 
promiscuous in all cases, or they must be different in differ- _ 
ent cases—that is, in different species, different sexes, dif- 
ferent stages of life. If they are different in different cases, 
then selection is a very unimportant matter, for the chief 
questions are evidently what are the differences and what 
made them differ. To deny that the variations have always 
been different in different cases is to deny the most evident 
facts; such denial might be possible when we consider only 
the difference between species, but it is impossible when 
we study the differences between the sexes in the same 
species and between different stages in the same individual. 
In all cases the variations correspond to differences in habits 
and mode of life, and in many cases are of the same kind 
as the changes known to be produced in the individual by 
special stimulation or special activity of organs; this is true 
of many and probably of all cases of adaptation. The gen- 
eral conclusion is that adaptation is not produced indirectly 
by the selection from indefinite variations, but directly by the 
influence of stimulation in modifying the growth of the 
parts or organs of the body.” 
Wallace * has suggested that the differences in color- 


OTHER THEORIES OF -SPECIES-FORMING, 355 


ation between males and females are due largely to the 

necessity of the better protection of the young 
te producing and (in the case of birds and mam- 

mals) young protecting and caring for female, 
and hence the acquirement on her part of a dull incon- 
spicuous protective colour-pattern. Wallace’s large ac- 
quaintanceship with birds and butterflies enables him to 
illustrate his theory by many apparently confirmatory ex- 
amples, but as soon as one stops to consider the matter 
thoughtfully the impossibility of the general or even wide 
application of this explanation of secondary sexual char- 
acters is at once apparent. It is necessarily limited to one 
single category of sexual differences. 

Barrett-Hamilton ** has noted that both sexes of the sal- 
mon (Onchorhynchus) become markedly discoloured during 
the spawning season. The discoloration is accompanied by 
overgrowth or hypertrophy, especially of the jaws. “I can- 
not believe,” he says, “that this is of an esthetic nature, since 
these phenomena terminate in the death of the fish. They 
seem to be, in fact, merely the outward symptoms of what, 
as I have persuaded myself from personal observation in 
Kamschatka, is a pathological condition accompanying, and 
perhaps resulting from, the growth of the ova and milt. 
I regard the whole metamorphosis as a purely excretory 
phenomenon resulting from the upsetting of the metab- 
olism due to the concentration of the whole vital force 
on the effort to produce the greatest possible amount of 
spawn. 

“May not such a state of things be invoked to explain the 
nuptial changes of our own salmon so strangely assumed 
before and lost after the breeding-season? Is it not possible 
that in the phenomena displayed by the spawning Oncho- 
rhynchus we may have a clue to the origin of the hitherto 
inexplicable temporary and permanent sexual characters 
of the vertebrates and even of some invertebrates, of which 


350 DARWINISM TO-DAY. 


it may be that the origin has been primarily excretory and 
only secondarily protective or esthetic?” 

The plain truth is that the satisfactory, all-explaining ex- 
planation of secondary sexual characters and sexual dimor- 
phism as a whole is yet to be formulated. 


APPENDIX. 


1 At some time between 1855 and 1865, Gregor Johann Mendel, 
an Augustinian monk in the small Austrian village of Brinn, car- 

Mendel and fried on pedigree cultures of peas and some other 
his work. plants in the gardens of his cloister. From this work 
he derived data that he read, together with his interpretation of 
their significance, before meetings of the Natural History Society 
of Briinn, and which, in the same year of their reading, 1865, were 
published under the title “Experiments in Plant-hybridisation,” in 
the Abhandlungen (Vol. IV.) of the society. Mendel was the son 
of a peasant and had been educated in Augustinian foundations and 
ordained priest. For two or three years he studied physics and 
natural science in Vienna, and refers to himself as a student of 
Kollar. He became Abbot of his cloister, and was for a time 
president of the Brinn Natural History Society. Such are the 
essential details of the education and situation of the man whose 
name will undoubtedly live forever in the annals of biological 
science. For the observations, experiments, and conclusions of 
Mendel on inheritance have taken their place already as matters of 
fundamental importance in the study of heredity. It would take 
us too far afield even to outline Mendel’s work and derived “‘princi- 
ples of heredity,” but the interested reader can find an admirable 
exposition and discussion of them (together with translations of 
Mendel’s own papers) in Bateson’s ‘‘Mendel’s Principles of Hered- 
ity,” 1902. 

For an excellent exposition of Mendel’s work and other similar 
work by botanists, see Lotsy, J. P., ““Vorlesungen tiber Descendenz- 
theorien,”’ Vol. I, chap. viii, 1906. 

Cuenot, in L’Année Biologique, Vol. VII, for 1902, pp. 58-77, 
gives an excellent review of the work of Mendel, de Vries, Cor- 
rens, and Tschermak; and a bibliography, relating to the so-called 
Mendelian laws of the principles of heredity. 

Bateson, in ‘‘Progressus rei Botannicae,”’ Vol. I, pp. 368-468, 1907, 
gives a complete abstract of the nature of the work and its results 
which has been done on the Mendelian problem from the time of 


OTHER THEORIES OF SPECIES-FORMING. ood 


Mendel to the present. The bibliography in connection with this 
paper is practically complete up to the date of its making. 

*Correns, C. G., “Uber Levkoyen-Bastarde, zur Kenntniss der 
Grenzen der Mendel’schen Regeln,” Botan. Centralbl., LXXXIV, 

References to P- 97, 1900; “Uber Bastarde zwischen Rassen von 
recent workon Zea Mays,” Ber. Deut. Bot. Ges., XIX, 211 (1901) ; 
Mendelism. “Bastarde zwischen Maisrassen, Bibliotheca Bota- 
Hicas stretts53, 1001-; “Uber Bastardirungs-Versuche mit Mirabilis- 
Sippen,” Ber. Deut. Bot. Ges., XX, 504-608, 1903. 

°T. E. Tschermak, “Uber kiinstliche Kreuzung bei Pisum sati- 
vum,” Zeitschr. f. d. Landwirthsch. Versuchswesen, III, 465-555, 
1900; “Weitere Beitrage tiber Verschiedenswerthigkeit der 
Merkmale bei Kreuzung von Erbsen und Bohnen,” ibid. IV, 641 ff., 
1901 ; “Uber Zuchtung neuer Getreiderassen mittelst kunstlicher 
Kreuzung,” ibid. IV, 1902. ‘Die Theorie der Kryptomerie und des 
Kryptohybridismus,” Beihefte z. Bot. Centralbl., XVI, 25 pp., 1903; 
“Weitere Kreuzungsstudien an Erbsen,” Zeitschrift f. d. Landwirth- 
Versuchswesen in Oesterr., 106 pp., 1904. 

*See Darwin, “Animals and Plants Under Domestication,” Vol. 
I, chap. i1, p. 104. “In some few instances new breeds [of sheep] 


Darwin on have suddenly originated; thus in 1791 a ram-lamb was 
race origin from born in Massachusetts, having short crooked legs and 
sports. a long back, like a turnspit dog. From this one lamb 


the otter, or ancon, a semi-monstrous breed, was raised; as these 
sheep could not leap over the fences it was thought that they would 
be valuable; but they have been supplanted by merinos, and thus 
exterminated. The sheep are remarkable from transmitting their 
character so truly that Colonel Humphreys never heard of ‘but one 
questionable case’ of an ancon ram and ewe not producing ancon 
offspring. When they are crossed with other breeds the offspring, 
with rare exceptions, instead of being intermediate in character, 
perfectly resemble either parent; even one of twins has resembled 
one parent and the second the other. Lastly, ‘the ancons have been 
observed to keep together, separating themselves from the rest of 
the flock when put into enclosures with other sheep.’ 

“A more interesting case has been recorded in the Report of 
the Juries for the Great Exhibition (1851), namely, the produc- 
tion of a merino ram-lamb on the Mauchamp farm, in 1828, which 
was remarkable for its long, smooth, straight, and silky wool. By 
the year 1833 M. Graux had raised rams enough to serve his whole 
flock, and after a few more years he was able to sell stock of his 
new breed. So peculiar and valuable is the wool, that it sells at 
25 per cent. above the best merino wool: even the fleeces of half- 
bred animals are valuable, and are known in France as the 


358 DARWINISM TO-DAY. 


‘Mauchamp-merino.’ It is interesting, as showing how generally 
any marked deviation of structure is accompanied by other devia- 
tions, that the first ram and his immediate offspring were of small 
size, with large heads, long necks, narrow chests, and long flanks, 
but these blemishes were removed by judicious crosses and selec- 
tion. The long smooth wool was also correlated with smooth horns; 
and as horns and hair are homologous structures, we can under- 
stand the meaning of this correlation. If the Mauchamp and ancon 
breeds had originated a century or two ago, we should have no 
record of their birth; and many a naturalist would no doubt have 
insisted, especially in the case of the Mauchamp race, that they had 
each descended from, or been crossed with, some unknown aborig- 
inal form.” 

The Paraguay cattle are a hornless race which is composed of 
the descendants of a hornless bull which was born in Paraguay in 
1770. 

A recent interesting case wholly parallel with those just recorded, 
is that of the Polled Herefords originating in 1889 in Kansas, U. 
S. A. (see Guthrie, W. W., “History of Polled Herefords,” in Proc. 
Am. Breeders’ Assoc., Vol. II, pp. 93-95, 1906). 

“In the fall of 1889, W. W. Guthrie, Sr., of Atchison, Kansas, 
now deceased, discovered among the calves that had been weaned 

Arecentex- at his ranch in Chase County, Kansas, one with Here- 
ample of race ford markings which was perfectly polled. In his 
origin from a herd were purebred Shorthorn as well as purebred 
sportin cattle tereford cows. Two purebred Hereford bulls were 
at the head of the herd. This calf was the product of a three- 
quarter Hereford and one-quarter Shorthorn cow by one of the 
two purebred Hereford bulls, Grateful 3d, No. 8,oo1, and Treasurer, 
No. 10,585. Discovery, as the calf was subsequently named, was a 
well-formed animal, with a good loin, and well-developed hind- 
quarters, and had the Hereford colour and markings, with body 
more on the type of the Shorthorn. At three years of age he 
weighed, without special feeding, 1,986 lbs. | 

“It then occurred to Mr. Guthrie that by using this animal he 
might in time establish a herd of polled Herefords, and that the 
experiment was at least worth trying. Shortly afterwards, he 
happened to meet on the train Chancellor Snow, of the Kansas 
State University, on his way to lecture before the Atchison High 
School on evolution, and during their several hours conversation 
discussed with him the proposition of animal architecture. The 
Chancellor agreed that the proposition of establishing a polled 
Hereford herd was one worth considering, and Mr. Guthrie deter- 
mined to carry out his ideas along this line. 


OTHER THEORIES OF SPECIES-FORMING. 359 


“When Discovery matured it was found that his calves from 
horned cows were all hornless. In 1893, a two-year-old bull and 
six heifers were selected and brought to Atchison County, where 
the experiment was carried on under the personal supervision of 
Mr. Guthrie and with very encouraging results. 

“On October 31, 1898, Mr. Guthrie purchased at the Kansas City 
Scott & Whitmann sale four purebred Hereford heifers. The calves 
from these horned heifers by a descendant of Discovery were found 
to be in every instance polled, only two showing scurs, scarcely 
noticeable, and loose in the skin. A number of purebred Hereford 
heifers were later obtained from the Funkhouser herd, and still 
later others from the Armour herd, and equally good results were 
obtained. 

“Right head of polled Herefords were exhibited by Mr. Guthrie 
at the Omaha Exposition, and, while these animals did not present 
the finished appearance of modern show cattle, not having been 
forced from date of birth, they attracted such attention that articles 
on the herd were published in the newspapers and periodicals 
throughout this country, and even in such far-away lands as Aus- 
tralia and New Zealand. 

“The desirability of Herefords without horns, the one objection 
which Hereford breeders had been willing to admit, becoming appa- 
rent, other Hereford breeders began to take notice of an occasional 
polled calf, freaks of nature as they were considered, appearing 
in their herds, and soon a brisk demand for polled bulls developed, 
animals being shipped as far north as South Dakota, and Wiscon- 
sin, and as far south as Texas. Breeders in many instances have 
reported that in their horned herds, after several years’ breeding, 
not a single calf had come with horns, and only occasionally would 
slight scurs, loose in the skin, appear.” ... 

“In December, 1904, four head of polled Herefords from West 
Virginia were exhibited at the International Live Stock Show at 
Chicago in connection with horned Herefords, and during the past 
season a larger number from the same State were exhibited through- 
out the eastern circuit of fairs. At the American Royal Cattle 
Show at Kansas City, last October, seven head from the original 
herd were exhibited. As a result of these exhibits, many horned 
Hereford breeders are now turning their attention to the subject of 
breeding Herefords without horns, and so great has become the 
demand for animals with which to start polled herds that at the 
last meet of the National Polled Hereford Breeders’ Association it 
was found that the members were unable to supply enough young 
bulls to meet the demand. 

“Quite a number of purebred Hereford calves, termed ‘freaks’ 


360 DARWINISM TO-DAY. 


or ‘sports, have been dropped in this country, and some have been 
kept. The President of the National Polled Hereford Breeders’ 
Association has a perfectly polled cow, the produce of one of his. 
purebred horned Hereford cows by a purebred horned Hereford 
bull, and has lately purchased a purebred polled Hereford bull. 
The original herd now contains two polled males and a number of 
polled females, descended direct from purebred Herefords. The 
above animals are registered in the American Hereford Record. 

“During a trip through England several years ago, Mr. Guthrie 
made inquiry among Hereford breeders and found that, while an 
occasional polled animal had been calved, they were considered as. 
freaks of nature by the owners and butchered.” 

* Bateson, Wm., ‘Materials for the Study of Variation,’ 1894. 

° Kdlliker, A. von, “Uber die Darwin’sche Schdpfungstheorie,” 
Zeitsch. f. wiss. Zool., Vol. XIV, pp. 174-186, 1864. 

Dall aw. eulog7: 

® Galton, Francis, ““Natural Inheritance,” p. 32, 1880. 

° Galton, Francis, loc. cit. p. 27, ““The distinction between primary 

Galton’s dis) and subordinate positions of stability will be made 
cussion of spe- clearer by the help of Fig. 1, which is drawn from a 
cific stability. model I made. The model has more sides, but Fig. 
1 suffices for illustration. It is a polygonal slab that can be made to 
stand on any one of its edges when set upon a level table, and is 





B A c B Davee 
FIG: I 


intended to illustrate the meaning of primary and subordinate 
stability in organic structures, although the conditions of these must 
be far more complex than anything we have wits to imagine. The 
model and the organic structure have the cardinal fact in com- 
mon, that if either is disturbed without transgressing the range 
of its stability, it will tend to reéstablish itself, but if the range is 
overpassed it will topple over into a new position; also that both 
of them are more likely to topple over towards the position of 
primary stability, than away from it. 

“The ultimate point to be illustrated is this. Though a long 
established race habitually breeds true to its kind, subject to small 


OTHER THEORIES OF SPECIES-FORMING. 368 


unstable deviations, yet every now and then the offspring of these 
deviations do not tend to revert, but possess some small stability 
of their own. They, therefore, have the character of sub-types, 
always, however, with a reserved tendency, under strained condi- 
tions, to revert to the earlier type. The model further illustrates. 
the fact that sometimes a sport may occur of such marked pecu- 
liarity and stability as to rank as a new type, capable of becoming 
the origin of a new race with very little assistance on the part of 
natural selection. Also, that a new type may be reached without. 
any large single stride, but through a fortunate and rapid succession 
of many small ones. 

“The model is a polygonal slab, the polygon being one that 
might have been described within an oval, and it is so shaped as 
to stand on any one of its edges. When the slab rests, as in Fig 1, 
on the edge A B, corresponding to the shorter diameter of the oval, 
it stands in its most stable position, and in one from which it is. 
equally difficult to dislodge it by a tilt either forwards or back- 
wards. So long as it is merely tilted it will fall back on being 
left alone, and its position when merely tilted corresponds to a simple 
deviation. But when it is pushed with sufficient force, it will tumble 
on to the next edge, B C, into a new position of stability. It will 
rest there, but less securely than in its first position; moreover, its: 
range of stability will no longer be disposed symmetrically. A com- 
paratively slight push from the front will suffice to make it tumble 
back, a comparatively heavy push from behind is needed to make it. 
tumble forward. If it be tumbled over into a third position (not 
shown in the figure), the process just described may recur with 
exaggerated effect, and similarly for many subsequent ones. If,. 
however, the slab is at length brought to rest on the edge C D, most 
nearly corresponding to its longest diameter, the next onward push, 
which may be very slight, will suffice to topple it over into an 
entirely new system of stability; in other words, a ‘sport’ comes 
suddenly into existence. Or the figure might have been drawn with 
its longest diameter passing into a projecting spur, so that a push 
of extreme strength would be required to topple it entirely over. 

“If the first position, A B, is taken to represent a type, the other 
portions will represent sub-types. All the stable positions on the 
same side of the longer diameter are subordinate to the first position. 
On whichever of them the polygon may stand, its principal tendency 
on being seriously disturbed will be to fall back towards the first 
position; yet each position is stable within certain limits. 

“Consequently, the model illustrates how the following condi- 
tions may co-exist: (1) variability within narrow limits without 
prejudice to the purity of the breed; (2) partly stable sub-types;: 


362 DARWINISM TO-DAY. 


(3) tendency, when much disturbed, to revert from a sub-type to 
an earlier form; (4) occasional sports which may give rise to new 
types.” 

*° Emery, C., “Gedanken zur Descendenz- und Vererbungstheorie,” 
Biolog. Centralbl., Vol. XIII, pp. 397-420, 1893. 

*2 Korschinsky, S., ‘“Heterogenesis und Evolution,” Naturw. 
Wochenscrift, Vol. XIV, pp. 273-278, 1899; also “Heterogenesis u. 
Evolution,” Flora, oder Allg. Bot. Zeit., Erganzungsbd. 89, pp. 240- 
368, 1901. 

**? De Vries, H., “Die Mutationstheorie,”’ Vol. I, 1901, Vol. II, 
1903. 

Retatnes th x De Vries, H., “Species and Varieties, Their 
discussions by Origin by Mutation” (ed. by MacDougal), 1905. 
de Vries of spe- **De Vries, H., “Die Mutationstheorie,’ Vol. I, 
cies-forming, p. 150, 1901. 

*® De Vries, H., “Die Mutationstheorie, Vol. I, p. 362, 1901. 

1® De Vries, H., “Species and Varieties,” p. 6. 

*T De Vries, H., “Species and Varieties,” pp. 8-9. 

18 De Vries, H., “Species and Varieties,” p. 10. 

*® De Vries, H., “Species and Varieties,” p. 13. 

*° For an excellent exposition and discussion of the de Vries muta- 
tion theory and mutations, see Lotsy, J. P., ““Vorlesungen tiber De- 
scendenztheorien,” Vol. I, chaps. xiv and xv, 1906. 

** Morgan, T. H., “Evolution and Adaptation,” pp. 294-295, 1903. 

** As evidence of the interest and favour with which American 
biologists have received the theory, the six addresses on “the muta- 

A tnerican tion theory of organic evolution” delivered before the 
opinion of the American Society of Naturalists at Philadelphia, 
mutations December 28, 1904, may be especially referred to. 
theory, These addresses by naturalists distinguished for their 
work in different phases of biology, as systematic and cecologic 
botany, cytology, human anatomy, animal cecology, etc., are printed 
in Science, N. S., Vol. XXI, pp. 521-543 (April 7, 1905), and from 
them I quote various paragraphs indicating some of the points 
of view of the speakers and some of the arguments advanced in 
favour of the theory. 

“On the whole, it appears that the formation of new breeds be- 
gins with the discovery of an exceptional individual, or with the 
production of such an individual by means of cross-breeding. Such 
exceptional individuals are mutations” (Castle, p. 524). 

“Modification of character by selection, when sharply alternative 
conditions (4. e., mutations) are not present in the stock, is an 
exceeding difficult and slow process, and its results of questionable 
permanency. Even in so-called ‘improved’ breeds, which are sup- 


OTHER THEORIES OF SPECIES-FORMING. 363 


posed to have been produced by this process, it is more probable 
that the result obtained represents the summation of a series of 
mutations rather than of a series of ordinary fluctuating variations. 
For mutations are permanent: variations transitory” (Castle, p. 
524). : 

“Tt is to my mind impossible to find any support for a theory of 
evolution by minute changes from the study of anatomical varia- 
tions. I should not venture to say, on the other hand, that they 
give any direct support to the theory of mutation: but, at least, they 
are not in disaccord with it” (Dwight, p. 532). 

“Tt seemed necessary to discuss ethological characters at some 
length for the purpose of vindicating their importance. Having 
attempted this, I may say that these characters seem to me to offer 
even fewer difficulties than the morphological characters to the 
acceptance of the mutation theory, for the reason that the ethological 
and psychological processes are conceived primarily as qualities 
and not quantities. Thus the psychical elements, 7. e., the simple 
feelings, cravings, and sensations, are disparate qualitative processes 
which cannot be derived from one another or from some more 
undifferentiated process. This is still more evident-in the case of the 
complex psychical phenomena. Similarly, instincts, with which 
ethology is most concerned, when resolved into their simplest com- 
ponents are seen to consist of discrete reactions which cannot be 
shown to arise from one another. Although, on the other hand, 
the measurable intensities and durations of the reactions are anal- 
ogous to the fluctuating structural variations, it is even more difficult 
for the psychologist to conceive of a particular feeling, craving, 
or sensation as arising from the greater or less intensity or dura- | 
tion of some other psychic process, than it is for the morphologist 
to conceive of the origin of new characters from the fluctuating 
variations of structure” (Wheeler, p. 539). 

“Mutation is even more urgently demanded for the explanation 
of many other instincts, especially those of symbiotic and parasitic 
species and of species with profound and sudden metamorphosis. 
In these cases, a particular activity, on which most often depends 
the life of the individual or of its progeny, has to be performed 
with a high degree of proficiency at its very phylogenetic incep- 
tion or it can be of no advantage to the individual or the race. 
Such cases, with which you are all familiar, have ever been the 
insurmountable obstacle to the evolution of instincts on the theory 
of fluctuating variations and natural selection. The theory of 
organic selection seems to me merely to conceal but not to over- 
come the difficulties. The mutation theory frankly avoids the diffi- 
culties even if it fails to throw any light on the origin of the muta- 


364 DARWINISM TO-DAY. 


tions and bundles this into the germ-plasma. It is, of course, no 
objection to the theory that it leaves something under the heavens to 
be accounted for. This is rather to be regarded as one of its chief 
virtues. As working naturalists we have reason to be most sus- - 
picious of the theories that explain everything’ (Wheeler, pp. 539- 
540). 

“In view of the amount of orderly and well-authenticated evi- 
dence now at hand, it may be regarded as demonstrated that char- 
acters, of appreciable physiological value, originate, appear in new 
combinations or become latent, in hereditary series of organisms, 
in such a manner as to constitute distinct breaks in descent” (Mac- 
Dougal, p. 540). 

23 Some of de Vries’s experiments and observations on the La- 
marck primrose have been repeated (with naturally some variation) 
in the New York Botanic Garden, by MacDougal and assistants. 
See MacDougal, D. T., “Mutation in Plants,” Amer. Nat., Vol. 
XXXVII, pp. 737-770, 1903; also, “Mutants and Hybrids of the 
CEnotheras,” by D. T. MacDougal, assisted by A. M. -Vail; 
G. H. Shull, and J. K. Smail, Pub. No. 24, Carnegie Inst. of Wash., 
1905. 

I am aware of the rather sweeping statements made by some 
biologists touching the probability of the origin by mutation of many 
species, or at least, races of animals and plants. For example, 
Castle \GScience, Ni.7S.,) Vol. XX] sp. 522; 1905) saystsaoomtar 
however, as these various sorts of evidence go, they indicate that 
the material used by breeders for the formation of new breeds con- 
sists almost exclusively of mutations.” And Davenport (Science, 
N. S., Vol. XXII, p. 372, 1905) says: “Undoubtedly many, if not 
most, of the characteristics of the races of domesticated animals and 
probably feral species have arisen by mutation.” He then refers, 
as.example, to the qualities that differentiate the races of poultry— 
feathered feet, rose comb, elongated tail, taillessness, silky 
feathers, frizzled feathers, cerebral hernia, polydactyl feet, albinism, 
and many others. But I have been assured by Luther Burbank, 
the most experienced and distinguished plant breeder in this country, 
that the many races of plants actually produced by him have not 
been derived from mutations. But on the contrary, that the selec- 
tion of small variations—a special abundance and variety of these 
variations usually being induced by hybridisation and by change of 
environment—has been his almost exclusively relied-on means for 
producing new forms of plants. As a matter of fact the cases 
actually adduced by upholders of the de Vriesian theory as supports 
for it are astonishingly few. Castle (Science, N. S., Vol. XXI, pp. 
522-523, 1905) calls attention to the sudden appearance of a super- 


OTHER THEORIES OF SPECIES-FORMING. 365 


numerary fourth digit on one of the hind feet of one of nine young 
produced by a certain pair of guinea-pigs. “Neither of the parents 
had such a digit, nor had I ever heard of the existence of such a 
character before, either in any of the wild Caviedze or among domes- 
ticated cavies or guinea-pigs. Further, I have been able to find 
no reference to such a thing in the literature of the group, though 
I have several times since found this same mutation in other herds 
of guinea-pigs. The mother of my four-toed pig never produced 
another similar individual, though she was the mother in all of 
thirty young. The father, however, who sired in all 139 young, 
had five other young with extra toes, but these were all by females 
descended from himself, so that it seems certain that the mutation 
had its origin in this particular male. By breeding together the four- 
toed young and selecting only the best of their offspring, I was able 
within three generations to establish a race with a well-developed 
fourth toe on either hind foot. This race was not created by selec- 
tion, though it was improved by that means.” Castle also had 
another mutation appear in a second family of guinea-pigs. “A 
few individuals were found to have hair about twice as long as 
that of their parents and grandparents. Intermediate conditions did 
not occur. Long-haired individuals mated together were found 
to produce only long-haired young, so that a new breed was already 
fully established without the exercise of any selection.” Casey 
(Science, N. S., Vol. XXII, p. 308, 1905) presents a number of 
facts touching the sudden appearance of certain molluscous genera 
in early Eocene strata, and in certain Lower Oligocene rocks, which 
seem to be evidence for the mutations theory. “At least, the 
mutation theory is evidently the best that has been advanced to 
account for these known facts.” Scott (Science, N. S., Vol. XXII. 
pp. 271-282) attempts to make out a case for the mutational origin 
of nine kinds of North American birds that, because of their rarity 
and the obscure character of the records of their occurrence, are 
mostly rather puzzling to ornithologists. (They are all included 
in the “hypothetical list” of the American Ornithologists’ Union 
Check-List.) But this attempt is robbed of much significance by 
Allen’s critical discussion of it (Science, N. S., Vol. XXII, pp. 431- 
434, 1905). Morgan (Harper’s Monthly Mag., Vol. CVI, p. 478) 
refers to the “japanned” turkeys, a kind of bronze-shouldered aber- 
ration that appears occasionally in flocks of turkeys, as “mutations.” 
These turkeys are called attention to by Darwin (“Variation of 
Animals and Plants Under Domestication,” Vol. I, p. 305). Indeed, 
more cases of such mutations are referred to and described by 
Darwin himself than by all those who have attempted recently to 
adduce examples, for the support of the mutations theory, of an 


366 DARWINISM TO-DAY. 


alleged case of sudden appearances of modified animals or plants 
that seem to breed true. But these infrequent prepotent sports, 
or discontinuous variations, do little to furnish any convincing 
foundation for de Vries’s theory. Far better than all of them are 
de Vries’s own long and carefully observed primrose mutations. 
Here, besides a few single mutations, were several that appeared 
in considerable numbers, which is a condition almost imperatively 
necessary for the successful propagation of a new organic type. 

A recent record of an alleged case of mutation is Schaffner’s, 
“A Successful Mutant of Verbena without External Isolation,” in 
Ohio Naturalist, Vol. VII, pp. 31-34, December, 1906. 

As Davenport (“The Mutation Theory in Animal Evolution,” 
Science, N. S., Vol. XXIV, pp. 556-558, November, 1906) puts it: ““The 
real argument for discontinuity in evolution is the occurrence of 
characteristics in nature that are discontinuous and which never 
show intergrades. The mere fact of discontinuity between species 
of the same genus is not sufficient to prove that they have arisen 
by mutation. It must be shown that the differential characters are 
in essence discontinuous. The practical way to get at the true 
nature of characteristics, whether continuous or discontinuous, is 
by their behaviour in inheritance. If, in cross-breeding, a char- 
acter tends to blend with the dissimilar character of its consort it 
must be concluded that the character can be fractionised and inter- 
grades are possible. If, on the contrary, the characteristic refuses 
to blend, but comes out of the cross intact, as it went in, the con- 
clusion seems justified that the characteristic is essentially integral 
and must have arisen completely formed, and hence discon- 
tinuously. 

“Using this criterion, I have of late been testing the application 
of the mutation theory to animals and have had an opportunity to 
examine the experiments of others. Some of the work has been 
done on the characteristics of domesticated ‘races,’ others on wild 
varieties. There seems to be no difference in the behaviour of 
characteristics of domesticated and wild varieties. The result is 
that most characteristics, but not all, fail to blend and are strictly 
alternative in inheritance. I interpret this to mean that the char- 
acteristic depends on a certain molecular condition that does not 
fractionise. The inference is that if the characteristic is incapable of 
gradations now it has always been so and hence must have arisen 
without gradations, 7. e., discontinuously. Examples of such discon- 
tinuous characteristics are the spots in the elytra of certain beetles, 
the crest on the canary, the form of the comb in poultry, extra toes, 
black plumage, and colour of iris. One who sees the striking 
failure of these characteristics and many others to be modified in 


OTHER THEORIES OF SPECIES-FORMING. 367 


any important way will feel convinced that they are not capable 
of forming intergrades and hence could not have arisen gradu- 
ally.” 

24C. B. Davenport (“Evolution Without Mutation,’ Jour. of 
Exper. Zool., Vol. II, pp. 137-143, 1905), in a recent short paper, 
adduces facts concerning the variation and evolution 


Davenport's : : 
5 of Pectens, which lead him to conclude that the races 


examples of spe- 


cies-originby of Pecten inhabiting different geographical regions * 


slight continu- are connected so plainly by integrating variations 
ous change. that there can be no question of mutations in con- 
nection with their origin. They must have arisen through evolu- 
tion by trivial variation. Davenport concludes his paper with the 
following summary: “The process of evolution has taken place by 
various methods and not always in the same way. It is not more 
justifiable to maintain that all evolution is by mutation than that 
evolution has always proceeded by slow stages. The best evidence 
for slow evolution is found in wide-ranging species which, while 
differing greatly at the limits of their range, exhibit all gradations in 
intermediate localities (Melospiza, Pecten); also in fossil series 
(Pecten eboreus and P. trradians) where the change from one hori- 
zon to the next is of a quantitative order. Thus evolution may take 
place without mutation.” 

Naturalists whose special field of study is systematic and fau- 
nistic rather than morphologic or experimental, seem to be slow to 

Marriain’s find much good in the mutations theory. Indeed, 
criticism of the some of them seem to be quick to find much that is 
mutations theory: j]] in it. For example, Merriam and Allen, deans of 
American faunistic students of birds and mammals, are both strong 
antagonists of the mutations theory. Merriam, in an address as 
chairman of the zoological section at the 1905 meeting of the Ameri- 
can Association for the Advancement of Science (“Is Mutation the 
Factor in the Evolution of the Higher Vertebrates?” Science, N. S., 
Vol. XXIII, pp. 241-257, 1906), shows by the use of illustrations 
drawn from the distribution and taxonomy of American chipmunks 
and ground squirrels that the mutations theory cannot by any 
means explain all species-forming. ‘My argument,” says Merriam, 
“is not that species of plants may not in rare cases arise in perpetu- 
ation of sport characters, as de Vries believes they do, but admitting 
this, my contention is that the overwhelming majority of plants, 
and so far as known, all animals, originate in the generally recog- 
nised way by the gradual development of minute variations. The 
theory of origin of species by mutation, therefore, far from being 
a great principle in biology, as some seem to believe, appears to be 
one of a hundred minor factors to be considered in rare cases as a 


‘na, preteens ane ener 


368 DARWINISM TO-DAY. 


possible explanation of the origin of particular species of plants, 
but so far as known, not applicable in the case of animals.” 

Certain naturalists even go so far as to express some doubt about 
the value of the mutations observed by de Vries in the primroses. 
This doubt touches two points. First, the possibility that the 
mutating primroses are not pure cultures, but are hybrids; second, 
that when an investigation of the wild primroses in their native 
locality (southern United States) is made it may be found 
that these primroses in true wild condition do not mutate. Touch- 
ing these two points, it should be said that de Vries has convinced 
himself that his cultures are pure, and has tried to discover the 
actual conditions existent among the primroses in their native 
habitat. As a matter of fact, the Lamarckian primrose seems to be 
practically extinct as a wild species. De Vries (“Uber die Dauer 
der Mutationsperiode bei Ginothera Lamarckiana,” Ber. Deutsch. Bot. 
Gesell., Vol. XXIII, pp. 382-387, 1905) found specimens of Génothera 
Lamarckiana in three botanical collections in the United States. 
‘These specimens were collected in Florida and Kentucky. How- 
ever, since these specimens were taken (the Florida ones in 1860) 
the species has not been observed, perhaps on account of lack of 
close observation, perhaps because actually disappeared. There- 
fore the question whether the Lamarckian primrose mutates in 
wild condition remains undecided. 

7° The most considerable critical discussion and analysis of the 
mutations theory is that made by Plate in his review of Morgan’s 

Plate's criti; | 2volution and Adaptation. (Plate, L., “Darwinismus 
cism of the mu- kontra Mutationstheorie,” Archiv f. Rassen- und Ge- 
tations theory. se]/schafts-Biologie, Vol. III, pp. 183-200, 1906.) In 
the course of his critical review of Morgan’s book (which book 
is at once an attack on Darwinism and an upholding of the muta- 
tions theory), Plate points out keenly and strongly the weak places 
in de Vries’s theory. As a general substitute for the natural selec- 
tion theory as an explanation of adaptation as well as species-form- 
ing, the mutations theory is open to many of the same objections as 
the Darwinian theories. Plate takes up, serially, Morgan’s claims 
for the mutation theory and readily shows their unconvincing char- 
acter. I quote some of this analysis, as follows: 

“Es ist von Interesse zu sehen, welche Griinde Morgan bestim- 
‘men, der Mutationstheorie trotz ihrer fundamentalen Mangel den 
Vorzug zu geben vor der alten Darwin’schen Auffassung. Auf. S. 
298 zahlt er die ‘Vorziige’ dieser Theorie auf, die aber meines 
Erachtens alle vor der Kritik nicht standhalten. 

““T. Da die Mutationen von Anfang an vollstandig ausgebildet 
auftreten, fallt die Schwierigkeit fort, die Anfangsstadien in der 


OTHER THEORIES OF SPECIES-FORMING. 369 


Entwicklung eines Organs zu erklaren, und da das Organ sich 
erhalten kann, selbst wenn es keinen Wert fur die Rasse hat, kann 
es durch spatere Mutationen weiter entwickelt werden und schliess- 
lich eine wichtige Beziehung zum Leben des Individuums erlangen.’ 

“Die erwahnte Schwierigkeit, die Anfangsstadien niitzlicher Struk- 
turen und Organe nach der Darwin’schen Auffassung zu erklaren, 
lasst sich nicht leugnen, aber sie ist, wie ich in dem oben erwahnten * 
Buche gezeigt zu haben glaube (S. 34-51), zu tiberwinden, besonders 
dann, wenn man in der Vererbungsfrage Gegner von Weismann ist 
und annimmt, dass ein durch Generationen ausgeiibter Reiz sich in 
seinem Effekt allmahlich steigert (Prinzip der Orthogenese) und 
wenn man sich darttber klar ist—was Morgan vollstandig entgangen 
zu sein scheint—das der Konkurrenzkampf zwischen zwei Arten 
sehr oft nicht sofort, sondern im Laufe von Generationen bloss 
durch die grossere Fruchtbarkeit entschieden wird, diese aber kor- 
relativ durch geringfiigige morphologische Unterschiede und unbe- 
deutende Anderungen in der Lebensweise wesentlich beeinflusst 
werden kann. Durch die Mutationstheorie wird aber jene Schwie- 
rigkeit in keiner Weise gehoben, denn erstens stellen die Mutationen, 
wie auch Morgan zugibt, meistens geringfiigige Abanderungen dar, 
welche die morphologische Breite der Fluktuationen nicht wtber- 
treffen. Man kann also nicht annehmen, dass das Stadium der 
Nititzlichkeit mit einem Sprunge erreicht wird, dass etwa der 
Rollriissel des Schmetterlings plotzlich aus kauenden Kiefern 
hervorging. Es mussten also eine Anzahl Mutationen in ganz 
bestimmter Weise aufeinander folgen, was, wie eben schon ange- 
deutet wurde, nach unsern jetzigen Kenntnissen von diesen regel- 
und richtungslosen Variationen unmoglich ist. 

">. Die neuen Mutationen konnen in zahlreichen Exemplaren 
auftreten und von ihren verschiedenen Sorten werden diejenigen sich 
erhalten, welche festen Fuss fassen konnen. Da dieselben Muta- 
tionen zu wiederholten malen auftreten koOnnen, wird die Gefahr, 
durch Kreuzung mit der Stammform vernichtet zu werden, im Ver- 
haltnis zu der Zahl der neu auftretenden Individuen geringer.’ Dass 
eine neue Mutation bei ihrem ersten Auftreten sofort in zahlreichen 
Exemplaren erscheint, ist ein dausserst seltenes Vorkommnis. Mir 
ist aus der Literatur nur der eine Fall der Whiteschen Washington- 
Tomate bekannt, welche sofort zu 100% aus der Varietat Acme 
zwei Jahre hintereinander auf derselben Lokalitat entstanden sein 
soll. Die Mutationen der Gartenpflanzen sind alle von einer oder 
einigen wenigen Stammexemplaren ausgegangen, waren also extreme 


*Plate, L., “Uber die Bedeutung der Darwin’schen Selections- 
prinzip,” 1903. 


370 DARWINISM TO-DAY. 


Singularvariationen, und erst durch Isolation und Selbstbefruchtung 
hat man grossere Mengen von Individuen erzielt. Die zoologischen 
Mutationen weisen, soweit ihr Ursprung bekannt ist, immer auf 
ein Stammtier: so das 1791 in Massachusetts entstandene Otterschaf, _ 
die 1770 von einem hornlosen Stier ausgegangene Rinderasse in 
Paraguay und die Rasse der Mauchampschafe, welche 1828 zuerst in 
einem Lamm, das von Merino-Eltern abstammte, auftrat. Schwanz- 
lose Katzen, Ziegen mit 4 Hornern, Menschen mit 6 Fingern sind 
weitere Belege daftir, dass solche sprungartige Abanderungen 
grosste Seltenheiten sind. Da Selbstbefruchtung im Tierreich im 
allgemeinen als ausgeschlossen gelten kann, so konnen solche Falle 
nur durch grosste Inzucht und strengste Selektion zum Range einer 
Rasse erhoben werden. Correns,* der selbst grosse Verdienste um 
die Erkenntnis der Mutationen sich erworben hat, schreibt (S. 34) 
tiber die Notwendigkeit der Selbstbefruchtung: ‘Es gentigt aber 
nicht, die Samen einer neu entstandenen Form zu sammeln und 
auszusaen; es muss auch daftir Sorge getragen werden, dass diese 
Samen ausschliesslich durch Selbstbefruchtung entstehen oder 
wenigstens, wenn mehrere abgeanderte Individuen verwendbar 
sind, durch Inzucht. Bei der Bestaubung der abgeanderten 
neuen Pflanzen mit dem Pollen einer zur alten unverandert 
gebliebenen Form gehorenden Pflanze, die der Wind oder die 
Insekten ausftihren konnen, entsteht ein Bastard zwischen der 
neuen und der alten Form, indem die letztere fast immer die 
erstere zunachst so vollkommen unterdruckt, dass der Bastard 
genau wie die alte Form aussieht. Die neue Form kann dann 
zwar in der folgenden Generation des Bastards wieder zum Vor- 
schein kommen; in der Praxis beurteilt man aber die Erblichkeit nach. 
der ersten Generation.’ Wenn also in der freien Natur eine einzelne 
Mutation auftritt, so wird sie als Regel mit der Stammform sich 
kreuzen und Bastarde erzeugen, die entweder nach dem Mendelschen 
Gesetz wie die Stammform aussehen oder den neuen Charakter in 
abgeschwachtem Grade besitzen. Die meisten von diesen Bastarden 
werden sich wieder mit der unveranderten Stammform kreuzen, da 
deren Individuen weitaus in der Majoritat sind, und so muss der 
neue Charakter in einigen Generationen wieder ausgeléscht werden, 
selbst wenn er in der ersten Zeit in einzelnen Individuen ab und zu 
zum Vorschein kommt.t Es gilt also meines Erachtens fiir die 
Mutationen dieselbe Regel wie fiir die Fluktuationen: Singular- 


* Correns, C., ‘““Experimentelle Untersuchungen iiber die Entste- 
hung der Arten auf botan. Gebiet.” Diese Zeitschr., I, 1904, S. 
27-52. Wie man sieht, vertritt Correns hier die Dominanz der 
phyletisch alteren Form. 

7 Vgl. hierzu S. 185, Anm. 


OTHER THEORIES OF SPECIES-FORMING. 371 


variationen spielen bei der Evolution keine Rolle, sondern nur 
Pluralvariationen, wenn wir absehen von jenen vereinzelten Fallen, 
in denen ein giinstiger Zufall fur die Isolation der Singularvariation 
sorgt. Wahrend aber bei den Fluktuationen sich leicht eine neue 
Rasse bilden kann, da immer viele Individuen nach dieser oder jener 
Richtung vom Durchschnitt abweichen oder durch die dausseren 
Faktoren in gleicher Weise verandert werden, liegen die Verhaltnisse 
fur die Mutationen sehr viel ungiinstiger. 

“3. Wenn die Zeit der Geschlechtsreife bei der neuen Form 
abweicht von der der Elternform, vermag sich die neue Ari nicht 
mit der Elternform zu kreuzen, und da dieser neue Charakter von 
Anfang an vorhanden ist, wird die neue Form bessere Aussichten 
haben am Leben zu bleiben als wenn der Zeitunterschied der Ge- 
schlechtsreife erst allmahlich erworben werden musste.’ Morgan 
erwahnt hier eine ganz spezielle Form der sexuellen Isolation. Man 
braucht jedoch nicht anzunehmen, dass dieselbe von den Fluktua- 
tionen allmahlich erworben wird; sie ist entweder von vornherein 
da, d. h. die neue Varietat wird in der Mehrzahl ihrer Individuen 
frither oder spadter geschlechtsreif als die Stammform, oder diese 
Schranke tritt tiberhaupt nicht auf. In diesem Punkte verhalten 
sich also die Fluktuationen genau so wie die Mutationen. 

““4. Die neuen Arten, welche erscheinen, konnen in einigen 
Fallen schon an eine andere Umgebung angepasst sein als die von 
der Stammform bewohnte; in diesem Falle werden sie von Anfang 
an isolirt sein, was einen Vorzug bei der Vermeidung der schlechten 
Einfliisse der Kreuzung bedeutet.’ Auch diese biologische Isolation 
gilt nattirlich in demselben Masse fur die Fluktuationen, ja sie muss 
bei ihnen eine weit grossere Rolle spielen, denn nach der Darwin- 
’*schen Auffassung wandern gewisse Individuen allmahlich in ein 
neues Wohngebiet ein und passen sich auf Grund ihrer Variabilitat 
an dieses im Laufe von Generationen an. Wenn aber unter den 
Exemplaren einer in der Ebene lebenden Art plotzlich einige muta- 
tive Individuen auftreten, welche fiir das Leben im Gebirge einge- 
richtet sind, so ist gar nicht zu verstehen, wie solche Mutationen 
sofort die ihnen zusagende Wohnstatte resp. Lebensweise auffinden. 

““s. Es ist wohl bekannt, dass die Unterschiede verwandter 
Arten zum grossen Teile Differenzen unwichtiger Organe sind, und 
dies steht in Harmonie mit der Mutationstheorie, bildet aber eine 
der wirklichen Schwierigkeiten der Selektionstheorie. 

“6. Nutzlose oder selbst leicht schadliche Charaktere konnen als 
Mutationen auftreten und sich erhalten, wenn sie die Fortdauer der 
Rasse nicht ernstlich beeinflussen.’ 

“Morgan muss sich wirklich sehr wenig in die Darwinischen 
Gedanken eingearbeitet haben, wenn er nicht einsieht, dass die 


372 DARWINISM TO-DAY. 


Selektionstheorie ttber den Ursprung der Variationen tberhaupt 
nichts aussagt, sondern diese einfach als gegeben hinnimmt, mdgen 
sie nur durch aussere Faktoren oder unbekannte innere Ursachen 
hervorgerufen werden und mogen sie nutzlich, schadlich oder 
indifferent ausfallen. In dieser Hinsicht steht sie auf demselben 
Boden wie die Mutationstheorie, welche gleichfalls den Ursprung 
der Mutationen nicht aufklart, sondern diese als plotzlich vorhanden 
ansieht. Die Selektionstheorie sucht uns nur klar zu machen, wie 
durch den Kampf ums Dasein die komplizirten nititzlichen Ein- 
richtungen, die Anpassungen, allmahlich entstehen konnten, und da 
nahverwandte Arten haufig in dem Grade der Ausbildung solcher 
Anpassungen—man denke z. B. an die Unterschiede zwischen dem 
indischen und afrikanischen Elefanten im Bau der Riisselspitze 
und der Ohren—voneinander abweichen, macht sie bis zu einem ge- 
wissen Grade auch den ‘origin of species’ verstandlich.* Morgan 
wirft in seinem Buche immer und immer wieder ganz unberechtigter 
Weise dem Darwinismus vor, er behaupte ‘That adaptations have 
arisen because of their usefulness.’ Selbst die extremsten Anhanger 
Darwins haben immer nur gesagt: gewisse Variationen bleiben 
erhalten, weil sie ntitzlich sind, und indem eine niitzliche Stufe zu 
der andern allmahlich addirt wird, entstehen schliesslich jene 
auffallenden Einrichtungen, die wir ‘Anpassungen’ nennen. Genau 
denselben Standpunkt nimmt die Mutationstheorie ein. Auch fir 
sie ist der Kampf ums Dasein—dieses Wort wie bei Darwin im 
weitesten Sinne genommen—das oberste regulatorische Prinzip der 
organischen Natur, welches die dauerfahigen Mutationen von den 
schadlichen sondert, dadurch die Evolutionen in ganz bestimmte 
Bahnen drangt und langsam die Entstehung der Anpassungen er- 
moglicht. Dadurch dass der Kampf ums Dasein das ‘Uberleben des 
Passendsten’ bedingt, schafft er etwas Positives und macht uns 
die mit dem Wechsel der Lebensweise und Umgebung stets wech- 
selnden Formen der Anpassungen verstandlich.” 

*° Klebs, the eminent plant physiologist, keenly criticises the muta- 
tions theory in his paper on “Willkirliche Entwicklungsanderungen 
bei Pflanzen,” 1903. See also Copeland, E. B., “The Variation of 
Some California Plants,’ Botan. Gaz. Vol. XXXVIII, pp. 401-426, 
1904. In this paper the author describes some striking aberrant forms 
of oak and fern leaves, but shows that between these mutation-like 
forms and the modal forms intergrading steps exist. Copeland 


* Es ist also nicht richtig, wenn Morgan (S. 454) von der Dar- 
win’schen Theorie behauptet, sie werfe die Frage des Ursprungs 
der Arten zusammen mit der des Ursprungs der Anpassungen. 
ang Probleme konnen zusammenfallen, aber sie brauchen es 
nicht. 


OTHER THEORIES OF SPECIES-FORMING. (373 


discusses keenly the mutations of de Vries and finds in them noth- 
ing radically different either in character or behaviour from the 
Darwinian fluctuating variations. 

7 Conklin, E. C., Science, N. S., Vol. XXI, p. 525, 1905. 

7° Morgan, “Evolution and Adaptation,” p. 292, 1903. 

*° Morgan, “Evolution and Adaptation,” pp. 298-299, 1903. 

PA anhctn °° Emery, C., “Gedanken zur Descendenz- und 
theories explain- Vererbungstheorie,” Biolog. Centralblatt, Vol. XIV, 
ing secondary PP. 397-420, 1803. 
sexual characters: 1 Cunningham, J. T., “The Species, the Sex, and 


perianal, Natural Science, Vol. XIII, pp. 184-192, 233-239, 
1808. 


*? Wallace, A. R., “Tropical Nature,” 1878. 

** Barrett-Hamilton, G. E. H., “Note on a Possible Mode of Origin 
of some Nuptial and Sexual Characters in Vertebrates,’ Anatom. 
Anzeig., Vol. XVIII, pp. 47-48, 1900. 


GHAPTERSX If. 
DARWINISM’S PRESENT STANDING, 


A RIVER rises froma perennial spring on the mountain side; 
gravitation compels the water to keep moving, and rock 
Natural selec- Walls, intervening hills, and soft loam banks 
epee determine the course of the stream. The living 
descent. stream of descent finds its never-failing primal 
source in ever-appearing variations; the eternal flux of 
Nature, coupled with this inevitable primal variation, com- 
pels the stream to keep always in motion, and selection 
guides it along the ways of least resistance. Although there 
can be no modification, no evolution, without variation, yet 
neither can this variation, whatever its character and extent, 
whether slight and fluctuating, large and mutational, de- 
terminate or fortuitous, long compel descent to go contrary 
to adaptation. And the guardian of the course is natural 
selection. Selection will inexorably bar the forward move- 
ment, will certainly extinguish the direction of any ortho- 
genetic process, Nagelian, Eimerian, or de Vriesian, which is 
not fit, that is, not adaptive.’ Darwinism, then, as the natural 
selection of the fit, the final arbiter in descent control, 
/ stands unscathed, clear and high above the obscuring cloud 
of battle. At least, so it seems to me. But Darwinism, as 
the all-sufficient or even most important causo-mechanical 
factor in species-forming and hence as the sufficient ex- 
planation of descent, is discredited and cast down.*’ At 
least, again, so it seems to me. But Darwin himself claimed 
no Allmacht for selection. Darwin may well cry to be saved * 

from his friends! 


374 


DARWINISM’S PRESENT STANDING. 375 


The selection theories do not satisfy present-day biolo- 
gists* as efficient causal explanations of species-trans- 

Mardral formation. ‘The fluctuating variations are not 
selection nota sufficient handles for natural selection; the 
Bit esanae hosts of trivial, indifferent species differences 
forming. are not the result of an adaptively selecting 
agent. On the other hand the declarations of Korschinsky, 
Wolff, Driesch, and others that natural selection is non- 
existent, is a vagary, a form of speech, or a negligible influ- 
ence in descent, are unconvincing; they are unproved. 

And these bitter antagonists of selection are especially un- 
convincing when they come to offer a replacing theory, an 

aa alternative explanation of transformation and 
of the replacing descent. To my mind every theory of hetero- 
eee: genesis, of orthogenesis, or of modification by | 
the transmission of acquired characters, confesses itself ulti-| 
mately subordinate to the natural selection theory. How- 
ever independent of selection and Darwinism may be the 
beginnings of modification, the incipiency of new species 
and of new lines of descent; even, indeed, however neces- 
sary to natural selection some auxiliary or supporting 
theory to account for the beginnings of change confessedly 
is, the working factor or influence postulated by any such 
auxiliary theory soon finds its independence lost, its influ- 
ence in evolution dominated and controlled by natural selec- 
tion. As soon as the new modifications, the new species 
characters, the new lines of descent, if they may come so 
far, attain that degree of development where they have to 
submit to the test of. utility, of fitness, just there they are 
practically delivered over to the tender mercies of selection. 
No orthogenetic line of descent can persist in a direction 
not adaptive, that is, not fit, and certainly no present-day 
biologist is ready to fall back on the long deserted stand- 
point of teleology and ascribe to heterogenesis or ortho- 
genesis an auto-determination toward adaptiveness and 


376 DARWINISM TO-DAY. 


fitness. Modification and development may have been 
proved to occur along determinate lines without the aid of 
natural selection. I believe they have. But such develop- 
ment cannot have an aim; it cannot be assumed to be 
directed toward advance; there is no independent progress 
upward, 7. e., toward higher specialisation. At least, there 
is no scientific proof of any such capacity in organisms. 
Natural selection *® remains the one causo-mechanical ex- 
planation of the large and general progress toward fitness; 
the movement toward specialisation; that is, descent as we 
know it. 

But what Darwinism does not do is to explain the begin- 
nings of change, the modifications in indifferent characters 

An explanation and in indifferent directions. And all this is 
Aes Sm tremendously important, for there are among 

ge is 

needed, animals and plants hosts of existent indifferent 
characters, and many apparently indifferent directions of 
specialisation. As to the obvious necessity of beginnings 
nothing need be said. What is needed, then, is a satisfactory 
explanation of the pre-useful and pre-hurtful stages in the 
modifications of organisms: an explanation to relieve Dar- 
winism of its necessity of asking natural selection to find 
in the fluctuating individual variations a handle for its 
action; an explanation of how there ever comes to be a 
handle of advantage or disadvantage of life-and-death- 
determining degree. With such an explanation in our 
possession—and whether any one or more of the various 
theories proposed to fill this need, such as Eimerian 
orthogenesis, de Vriesian heterogenesis, Rouxian battle of 
the parts, or Weismannian germinal ‘selection, etc., give 
us this explanation, may be left for the moment undebated 
—with such a satisfactory explanation, I say, once in our 
hands, we may depend with confidence on natural selection 
to do the rest of the work called for by the great theory 
of descent. Among all the divergent lines of development 


DARWINISM’S PRESENT STANDING, 377 


and change, instituted by this agent of beginnings, natural 
selection will choose those to persist by saying No to those 
that’ may not. And the result is organic evolution. 
But all this is equivalent to saying that there are other 
important factors in descent than selection, and that as to 
beled beth the beginnings of descent—and this is species- 
variation and the forming—these other factors are the more im- 
Benth chiat portant ones. Which I believe is true*‘ The 
factors in spe- Causes of variation and the means of segrega- 
cles-forming» ~~ tion or isolation are the chief factors in actual 
species-forming.” Certainly the mutations theory is not yet 
ready to offer itself as an explanation of adaptation, how- 
ever confidently it may claim to be enrolled among species- 
forming factors. The very same objections that have served 
to topple down selection from its high seat of honour, can be 
directed immediately and effectively against this latest claim- 
ant for recognition as the Great Cause of descent. Nor can 
geographical isolation explain modification where adaptation 
is included. Nor can Lamarck’s beautiful explanation of 
adaptation claim validity, until the actuality of its funda- 
mental postulate, the carrying over of ontogenic acquire- 
ments into phylogeny, be proved. And so with Buffon and 
St. Hilaire’s influence of the ambient medium, and Eimer’s 
modifying factors. Nor can any Nagelian automatic per- 
fecting principle hold our suffrage for a moment unless we 
stand with theologists on the insecure basis of teleology. 
No, let no ambitious student hesitate to take up the 
search for the truth about evolution from the notion that 
Theunknown PiClogy is a read book. The “Origin of Spe- 
factors of evolu- cCies’’ was the first opening of the book—that 
roe the world recognised at least; poor Lamarck 


opened the book but could not make the world read in it— 


and that time when it shall be closed because read through 
is too far away even to speculate about.’ With Osborn * let 
us join the believers in the “unknown factors in evolution.” 


378 DARWINISM TO-DAY. 


Let us begin our motto with Jgnoramus,; but never follow 
it with Jgnoribiumus. 

Now if we do not know, but want to know, and are willing 
to make an attempt toward knowing, where shall our energy 

Prime needs 01 €XPloration and discovery be first directed? . 
of evolution To what particular points or aspects of the 
anys causes-of-evolution problem shall we give our 
first attention, what fields of study first invade? ‘ What, in a 
word, is the principal desideratum in present-day investiga- 
tion of evolution? I should answer, the intensive study of 
variability. Not alone of the statics of variation but of its 
_ dynamics.” Indeed, above all its dynamics. The experimental 
study of the stimuli, external and internal, the influences, 
extrinsic and intrinsic, which are the factors and causes of 
variation,—this is the great desideratum; this the crying call 
to the evolution student. Experiment in variation study 
includes controlled modification of ontogeny (experimental 
development) and controlled modification of phylogeny 
(pedigreed breeding). In the study of variation statics, 
biometry is the greatest advance in modern methods, and 
the essential basis of biometric study, namely, quantitative 
and statistical data, must have its part in the investigation 
of variation dynamics. But in entering the realm of the 
causal study of variability, “we must not,’ as Roux has 
clearly pointed out, “conceal from ourselves the fact that 
the causal investigation of organism is one of the most 
difficult, if not the most difficult, problem which the human 
intellect has attempted to solve, and that this investigation, 
like every causal science, can never reach completeness, 
since every new cause ascertained only gives rise to fresh 
questions concerning the cause of this cause.” 

I believe that the neglect on the part of the selectionists to 
pay sufficient attention to the origin and causes of the varia- 
tion which is such an indispensable basis of their theory, has 
been one of the most obvious reasons for the present strong 


DARWINISM’S PRESENT STANDING. 379 


reaction against the selection theories.. Thankfully accept- 
ing the bricks and stones handed to them they have builded 
Neglectof a house of great beauty: but with stones of 
cae eraeaa tens different shape a house of quite different ap- 
tion, pearance might have been built. Is it not a 
cause for wonder that the selection masons have not been 
more inquisitive concerning the whence and why of this 
magical supply of just the needed sort of material at just the 
right time? As a matter of fact, Darwin himself gave 
serious attention to the origin of his always-ready varia- 
tions, but his tremendous undertaking was too nearly super- 
human already to permit him to add to it an adequate 
attention to the problem of causes. But that same excuse 
does not attach to his followers. And it is, I repeat, largely 
this neglect to strive to penetrate the so-far unrent veil of 
obscurity lying over the beginnings of species change that 
has contributed to the growing revolt against the Allmacht 
of the selection dogma. ' Who would in these days have a 
following for his explanation of species origin must include | 
in his theory some fairly satisfying explanation of the first | 
visible beginnings of modification. 
’ Then, after the explanation of the why and how of varia- 
bility, comes the necessity of explaining the cumulation of 
this variability along certain lines, the first visi- 
ble issuance of these lines being as species,’and 
later becoming more and more pronounced as 
courses of descent. This explanation has got to begin lower 
down in phyletic history than natural selection can begin. 
Before ever there can be utility and advantage there must 
have come about a certain degree of heaping up, of cumu- 
lating, of intensifying variations. What are these factors? 
They are possibly only two: (1) orthogenetic or deter- 
minate variation as the outcome of plasm preformation or 
of epigenetic influences, and (2) the segregation of similar 
variations by physiologic or topographic conditions. Hence, 


How is varia- 
tion cumulated ? 


380 DARWINISM TO-DAY. 


next to the cause or origin of variability the great desider- 
atum is a knowledge of the means of cumulating and direct- 


ing variability. And both these great fundamental needs 
/of a satisfactory understanding of organic evolution seem 


to me to be wholly unreferred to in the theory of natural 
selection. To be sure the control and cumulation of such 
large differences among organisms and species as are posi- 
tively sufficient to determine the saving or the loss of life 
are explicable by selection. And this factor is sooner or later 
in any phyletic history bound to step in and probably 
be the dominant one. But a species, or a character, will 


always have a longer or shorter preselective existence and 
history, and it is precisely these days before the Inqui- 
sition of which we demand information. For of one thing 
we are now certain, and that is, that evolution and the origin 


of species have both their beginnings and a certain period 
of history before the day of the coming of the Grand 
Inquisitor, selection. 

Finally there is still another desideratum and one whose 
seeking will carry us into dangerous country. For while 
there may be and are selectionists who might allow us to 
fumble about in the darkness of preselective time for first 
causes, there is probably none who will allow us to ques- 
tion his right to explain that other element in evolution be- 
sides species transformation, namely, adaptation, or, as the 
Germans ‘untranslatably put it, Zweckmdssigkeit. But by 
no means all biologists ° find in natural selection a sufficient 
explanation of adaptation. | 

In the visible expression of organic evolution are two 
chief elements, one the variety of life kinds, the existence of 

The great species, the reality of lines of descent; and the 
need ofexplain- Other the adaptedness and adaptiveness of these 
ing adaptation, Jife kinds. The varieties of organic kinds show 
themselves adapted in structure and function to the varie- 
ties of environment and life-conditions. ‘ Hence, the task 


DARWINISM’S PRESENT STANDING. 381 


of an evolution explanation is a double one; it must explain 
not only diversity or variety in life, but adaptive diversity 
or variety.~ And there is no gainsaying to the selection 
explanation its claim to stand among all proposed explana- 
tions of adaptation as that one least shaken by the critical 
attack of its adversaries. However mightily the scientific 
imagination must exert itself to deliver certain difficult 
cases into the hands of selection, and however sophisticated 
and lawyer-like the argument from the selection side may 
be for any single refractory example, the fact remains that 
the selectionist seems to be able to stretch his explanation 
to fit all adaptations with less danger of finding it brought 
up against positive adverse facts than is possible to the 
champion of any other so far proposed explanation.’ The 
explanation of adaptation by natural selection steers wide 
of teleology on one hand and of unproved assumptions con- 
cerning heredity on the other. “ The protoplasmic conscious- 
ness of Cope and the automatic perfecting principle of 
Nageli and those of his manner of explanation, are only 
indirect ways of attributing to natural forces visions and 
anticipations of what does not yet exist; while the influence 
of the ambient medium of St. Hilaire and of the extrinsic 
factors of Eimer, and the impressing photographically on 
the species and the carrying over into phylogeny, with 
approximate identity, of characteristics and modifications 
acquired ontogenetically by the individual as a result of 
functional stimulation—all these are assumptions not only 
apparently unproved, but in the light of our present 
- knowledge of the mechanism of heredity seemingly un- 
_ provable. 

Yet the explanation of species transformation and of 
adaptation by the introduction into phylogeny of modifica- 
tions (reaction effects) arising in the individual during its 
ontogeny, has to its credit a certain logical proof, or 
basis, which has great validity in my mind, and yet which 


ah NL teh a Men hin hn WEF 


382 DARWINISM TO-DAY. 


has enjoyed little general recognition and almost no em- 
phasis from supporters of Lamarckism or neo-Lamarckism. 
As the great strength of the natural selection explanation of 
species-change and adaptation lies precisely in the logical 
nature of its premises and conclusions rather than on scien- 
tific observation and experiment,’ it certainly is not unfair 
to emphasise any similar kind of proof tending to support 
the Lamarckian type of explanation. 


The logical proof that I refer to is simply this: It is ay} 
universally admitted fact that environment and functional — 
A logical proof stimulation can and do modify organisms dur- || 


for the introduc- . 


tion into phylog- IN their lifetime, and that this modification’ 


eny of adaptive jis usually plainly adaptive.“ It is also an 
ontogenetic 


changes, admitted fact that species differences or modi- 


fications are often identical with these cntogenetic modifica- 
jtions. That is, that under similar environment or life 


conditions species modification often follows the same lines 
as ontogenetic or individual modification. Now when we 
recall the possibilities of the hosts of ways in which the 
necessities of adaptation to varying environment might be 
met by selection among nearly infinite fortuitous variations, 
and yet see that exactly that means or line or kind of adapt- 
ive change occurs, which in the case of the individual is 
plainly and confessedly a direct personal adaptive reaction 
to varying environment, is it not the logical conclusion that 
the species change and adaptation is derived, not by the 
chance appearance of the needed variation, but by the com- 
pelled or determined appearance of this variation? In other 


_words when species differences and adaptations are identical 
with differences and modifications readily directly produci- 
ble in the individual by varying environment, are we not 
| justified, on the basis of logical deduction, to assume the 


transmutation of ontogenetic acquirements into phyletic 
acquirements, even though we are as yet ignorant of the 
physico-chemical or vital mechanism capable of effecting the 


FOr 


(oerenyeynepresenesenaninenent 


DARWINISM’S PRESENT STANDING. 383 


carrying over? Has natural selection’s claimed capacity to 
effect species change, unseen by observer, untested by exper- 
imenter, any better or even other proof of actuality than 
that just offered on behalf of species modification as a direct 
result of the stimulus of varying environment and func- 
tional exercise? I cannot see that it has. 

And this kind of argument, based half on observed facts 


and half on deduction, may be extended even farther on, 


The same kind 
adaptive change, 


duced directly in response to environment that are not 
plainly adaptive; many, indeed, between which and the 
environmental conditions that produce them no reasonable 
relation is apparent; no relation, that is, that would be ex- 
actly expected or could be foretold until empirically deter- 
mined. In other words, many apparently non-significant 
ontogenetic differences or variations appear as direct result 
of environmental influence or stimulus. For example, indi- 
viduals of certain species of the Crustacean phyllopod genus 
Artemia show marked structural differences when grown 
in salt water of varying density. These differences are in 
the size and shape of the plate-like lateral gills, the seg- 
mentation of the post-abdomen, the length of the caudal 
flaps (telson) and the hairiness of these flaps. The size of 
the whole body is also affected, individuals developing in 
water of higher density being markedly smaller than those 
which have been grown in less dense water. Now of all 
these differences only two seem to have what I call a rea- 
sonable relation to the environmental differences. The in- 
creased proportional size of the gills shown by the Artemias. 
grown in denser water appears to be a regulatory change 
connected with the smaller amount of oxygen in the water, 
and the decreased size of the body may similarly be con- 
ceived by some to be an expected concomitant of the 


behalf of the theory that species change is the 
of proof fornon- direct reaction to environmental conditions. | 
For there are many ontogenetic variations pro- | 


384 DARWINISM TO-DAY. 


denser water condition. But what of the extra abdominal 
segment, the longer telson projections and their increased 
hairiness, all of which as shown by Schmankewitsch ° (how- 
ever mistakenly this investigator may have interpreted his 
results as examples of actual species modification) and 
Anikin ° for Artemia salina and by the writer’’ for Artenna 
franciscanus, are the ontogenetic differences that varying 
density of salt water actually produces in individuals of a 
single Artemia species. These differences, these variations, 
are of the sort that I am calling non-significant, non-adapt- 
ive, non-reasonable. They would not be prophesied; they 
seem to have no reasonable correlation with the causes 
which produce them. But they are actually the results or 
effects of determined proximate causes which are extrinsic 
or environmental. If now the logical argument (based on 
identity of adaptive modification in individuals and in spe- 
cies) for the transmutation of ontogenetic changes into 
phyletic changes has any validity, then these non-adaptive, 
indifferent modifications may be transmuted as well as the 
adaptive ones, and thus hosts of trivial, non-adaptive indif- 
ferent species differences be explained on this Lamarcko- 
Eimerian basis as well as the obviously adaptive modifica- 
tions. But I am not insisting on this sort of argument too 
strongly. It is exactly the sort of argument upon which the 
theory of natural selection chiefly rests, and I have cer- 
tainly tried to make evident in this book my belief in the 
danger of the substitution of this sort of logical or meta- 
physical basis of belief in a theory for a scientific basis of 
observation and experiment. 

Finally, let us ask ourselves why we have adopted the 
common belief that our search for a cause of variability is a 

Asuggestim Search for some so far unknown, some quite 
concerning the new factor or force in biology? May it not be 
cause of varia- 
tion. that the factor is already familiar to us; so 
familiar indeed perhaps that we are esteeming it too simple 


DARWINISM’S PRESENT STANDING. 385 


and too obvious to play the role of the Great Desideratum, 
a causal factor of variability. 

When one attempts to picture the process of the making 
of a new individual, and follows the complex phenomena of 
fecundation, of embryology, and post-embryonic develop- 
ment, is it not impossible to conceive of the production of 
two identical individuals? In all the course of this develop- 
ment, from the first cleavage of the fertilised egg-cell on, 
it is practically impossible to repeat processes absolutely 
identically, hence to produce absolutely identical organs, 
parts, cells. Now the germ-cells have their very origin in 
a repeated complex process, mitotic cell division; they are 
produced as nearly alike as possible, but it is not possible 
to make them absolutely identical. 

Development, whether largely epigenetic or largely evo- 
lutionary, depends at least partly (probably largely) on the 
physical, 7. e., structural, character of the germ-cells. Slight 
differences in the germ-cells then would lead to considera- 
ble differences in the fully developed organ. If the differ- 
ences in the germ-cells happened, as would occasionally or 
rarely be the case, to be considerable, then the differences in 
the adults would be very considerable (mutations, sports, 
monsters, etc.). We know enough of the complex and 
epigenetic character of ontogeny to see plainly that identity 
among individuals, even of the same brood, is impossible. 

Variation, then, seems the necessary, the absolutely un- 
avoidable outcome of the conditions to which the developing 
individual is exposed. Indeed, all the individuals of a 
species might start (as fertilised eggs) exactly alike, and 
yet I cannot see how any two could come out alike. The 
inevitable slight differences in position, and hence in nutri- 
tion, in the results of the host of dividing and folding, in- 
vaginating and evaginating processes, the relations of each 
individual, whether in the mother’s body or out of it, to 
everything else outside of itself—all these are conditions 


386 DARWINISM TO-DAY. 


bound to vary a little between any two individuals. And as 
we know from the facts of experimental embryology that 
development is, partly at least, epigenetic in character, 1.e., 
depends on and is influenced by external factors, this in- 
evitable variation in influencing conditions is bound to pro- 
duce variations in the individuals. 

Is there, indeed, any need at all for assuming (1) any 
mysterious “tendency” of the germ-plasm to vary? and (2) 
that the individual (continuous) variation depends wholly on 
germ-plasm structure? Why cannot the simple fluctuating 
or Darwinian variations be chiefly the result of the inevitable 
variation in the epigenetic factors, which, when not intruded 
on by exceptional disturbances, would themselves follow the 
“law of error” and hence produce “law of error’ variabil- 
ity? All normal swingings of the variation pendulum in 
any part or character, between long and short, large and 
small, round and angular, smooth and rough, etc., etc., 
would result from the normal variation of the processes ; the 
larger (extremes of range) variations being the fewer be- 
cause the larger (extremes of range) variations in the 
ontogenetic processes would be the fewer. Exceptionally 
large epigenetic variations would produce exceptionally 
large variations in the individual—sports, mutations. 

Klebs,** as a result of his masterly experimental studies 
on modifications of plant development, comes to the 
conclusion that the only proved causes of variation are 
extrinsic influences stimulating, working through, or com- 
bined with, intrinsic conditions (not vitalistic, but physico- 
chemical). Similarly, Tower,’* from his protracted studies 
on the variations in certain insects, concludes that all these 
variations are caused by external stimuli working on the 
germ-plasm. 

If variation is thus simply the wholly natural and un- 
avoidable effect ** of this inevitable non-identity of vital 
process and environmental condition, why does not evolution 


DARWINISM’S PRESENT STANDING. 387 


possess in this state of affairs the much sought for, often 
postulated, all-necessary, automatic modifying principle an- 
Ra eeeeetccatiue tang preceding selection which must 
though not pur- effect change, determinate though not purpose- 
poseful change. 11> Nageli’s automatic perfecting principle is 
an impossibility to the thorough-going evolutionist seeking 
for a causo-mechanical explanation of change. But an 
automatic modifying principle which results in determinate 
or purposive change, that is, in the change needed as the 
indispensable basis for the upbuilding of the great fabric of 
species diversity and descent; is not that the very thing pro- 
vided by the simple physical or mechanical impossibility of 
perfect identity between process and environment in the case 
of one individual and process and environment in the case 
of any other? It seems so to me. 

But I do not know. Nor in the present state of our knowl- 
edge does any one know, nor will any one know until, as 
Brooks ** says of another problem, we find out. We are 
ignorant; terribly, immensely ignorant. And our work is, 
to learn. To observe, to experiment, to tabulate, to induce, 
to deduce. Biology was never a clearer or more inviting 
field for fascinating, joyful, hopeful work. To question life 
by new methods, from new angles, on closer terms, under 
more precise conditions of control; this is the requirement 
and the opportunity of the biologist of to-day. May his 
generation hear some whisper from the Sphinx! 


APPENDIX, 


1One of the most serious and detailed critical analyses of the 
selection theory, resulting in conclusions totally antagonistic to Dar- 

Wigand’s oriti- Winism, is that of the Marburg botanist, Prof. Albert 
cism of the selece Wigand, composing the three volumes entitled “Der 
tion theories. Darwinismus und die Naturforschung Newtons und 
Cuviers” (Vol. I, 1874; Vol. II, 1876; Vol. III, 1877). From the 
“Announcements” at the beginning of each volume I quote as 
follows: 


388 DARWINISM TO-DAY. 


From Vol. I. “Die hier dargebotene Kritik der Darwin’schen 
Lehre weist zunachst durch eingehende Prufung der hierher ge- 
horigen naturhistorischen Thatsachen nach, dass weder die Voraus- 
setzungen, von denen die Theorie ausgeht, noch ihre Consequenzen 
mit der wirklichen Natur tibereinstimmen, dass sie demnach den 
Anforderungen an eine wissenschaftliche Hypothese nicht entspricht. 
Vielmehr erweist sich dieselbe als eine philosophische Speculation, 
welche nicht nur die unserer Naturerkenntniss vorgezeichneten 
Grenzen iiberschreitet, sondern vor Allem die wichtigsten Grundsatze 
der wahren Forschung, wie sie durch die grossen Meister aufgestellt 
und in der bisherigen Entwickelung der Naturwissenschaft allgemein 
anerkannt und unbedingt maassgebend gewesen sind, insbesondere 
die Principien der Causalitat und der organischen Entwickelung, aufs 
grobste verleugnet. Demnach erkennt das vorliegende Werk seine 
Hauptaufgabe gerade darin, der bis dahin befolgten Forschungsweise 
gegenitiber jener neuesten Naturphilosophie ihr Recht zu wahren.” 

From Vol. II. ‘“Vermittelst der hierdurch gewonnenen Kriterien 
gelangt die Untersuchung in Betreff des Darwinismus zu _fol- 
gendem Ergebnis: Derselbe geht nicht bloss von falschen Voraus- 
setzungen aus, erweist sich nicht nur unfahig in Beziehung auf die 
versprochenen Leistungen, ist nicht nur verfehlt durch die princi- 
pielle Unmoglichkeit seiner Aufgabe, ist nicht nur eine der Natur- 
forschung fremdartige, rein speculative Operation, sondern indem 
derselbe das Princip der Causalitat und Entwickelung mit dem 
Zutfall und der Teleologie als Erklarungsgrunde vertauscht, erscheint 
er als eine der Naturforschung in ihrer Fundamentalmaxime wider- 
sprechende, darum dieselbe geradezu gefahrdende Verirrung, um 
so mehr als er unter ihrer Maske auftritt. Der Darwinismus ist 
einer jener Versuche, welche im Namen der Naturforschung die 
Naturforschung verderben.” 

From Vol. III. “Der vorliegende dritte Band, mit welchem dieses 
Werk abschliesst, hat zum Gegenstand nicht die dem Darwinismus 
zu Grunde liegende Theorie, sondern die concrete Gestalt, in welcher 
derselbe als eine fur unsere Zeit charakteristische culturhistorische 
Thatsache in die Erscheinung tritt. Insbesondere wird versucht, 
ein Bild von der Darwin’schen Schule als der Gesammtheit der die 
Transmutationstheorie vertretenden Auctoren und von der Art und 
Weise, wie sich die letztere im Lichte ihrer Bekenner darstellt, zu 
entwerfen. Hierbei ergibt sich, dass der Darwinismus mehr in einer 
ziellosen Zeitstromung und in einer wissenschaftlich nicht motivirten 
Stimmung der Geister als in einer bestimmt zu formulirenden Lehre 
besteht, und dass derselbe bereits in seinem eigenen Lager in allen 
wesentlichen Punkten wissenschaftlich tberwunden ist, und zwar in 
solcher Weise, dass in den widerstreitenden Ansichten der Darwin- 


DARWINISM’S PRESENT STANDING. 389 


janer doch zugleich der Keim ftir die allein richtige Auffassung der 
organischen Natur, wenn auch grossentheils unklar und unbewusst, 
verborgen liegt.” | 

A special answer to this exhaustive pleading of Wigand is offered 
by H. Spitzer in his “Beitrage zur Descendenztheorie und zur Metho- 
dologie der Naturwissenschaft,” 1886. 

* However, there still exist, especially in England, thorough- 
going Darwinians who see nothing serious in all this criticism of 
their great compatriot’s explanation of the origin of 


Lankester's ; é 
upholding of species. Lankester, one of the most prominent of 
Darwinism. English naturalists, said at York, last August (1906), 


in his inaugural address as president of the British Association for 
the Advancement of Science: “Under the title ‘Darwinism’ it is con- 
venient to designate the various work of biologists tending to estab- 
lish, develop or modify Mr. Darwin’s great theory of the origin of 
species. In looking back over twenty-five years it seems to me that 
we must say that the conclusions of Darwin as to the origin of 
species by the survival of selected races in the struggle for exist- 
ence are more firmly established than ever. And this because there 
have been many attempts to gravely tamper with essential parts 
of the fabric as he left it, and even to substitute conceptions for 
those which he endeavoured to establish, at variance with his 
conclusions. These attempts must, I think, be considered as having 
failed.” 

* “Physiologic. facts concerning the origin of species in nature 
were unknown in the time of Darwin. It was a happy idea to 

De Vries’s dis- Choose the experience of the breeders in the produc- 
cussion of species- tion of new varieties, as a base on which to build an 
forming by explanation of the processes of nature. In my opinion 
Tes Darwin was quite right, and he has succeeded in giv- 
ing the desired proof. But the basis was a frail one, and would not 
stand too close an examination. Of this Darwin was always well 
aware. He has been prudent to the utmost, leaving many points 
undecided, and among them especially the range of validity of his 
several arguments. Unfortunately this prudence has not been 
adopted by his followers. Without sufficient warrant they have laid 
stress on one phase of the problem, quite overlooking the others. 
Wallace has even gone so far in his zeal and ardent veneration for 
Darwin, as to describe as Darwinism some things, which, in my 
opinion, had never been a part of Darwin’s conceptions. 

“The experience of the breeders was quite inadequate to the 
use which Darwin made of it. It was neither scientific, nor critically 
accurate. Laws of variation were barely conjectured; the different 
types of variability were only imperfectly distinguished. The breed- 


390 DARWINISM TO-DAY. 


ers’ conception was fairly sufficient for practical purposes, but science 
needed a clear understanding of the factors in the general process 
of variation. Repeatedly Darwin tried to formulate these causes, 
but the evidence available did not meet his requirements. 

“Quetelet’s law of variation had not yet been published. Mendel’s 
claim of hereditary units, for the explanation of certain laws of 
hybrids discovered by him, was not yet made. The clear distinction 
between spontaneous and sudden changes, as compared with the 
ever-present fluctuating variations, is only of late coming into recog- 
nition by agriculturists. Innumerable minor points which go to elu- 
cidate the breeders’ experience, were unknown in Darwin’s time. 
No wonder that he made mistakes, and laid stress on modes of 
descent which have since been proved to be of minor importance 
or even of doubtful validity. 

“Notwithstanding all these apparently unsurmountable difficulties, 
Darwin discovered the great principle which rules the evolution of 
organisms. It is the principle of natural selection. It is the sifting 
out of all organisms of minor worth through the struggle for life. 
It is only a sieve, and not a force of nature, no direct cause of 
improvement, as many of Darwin’s adversaries, and unfortunately 
many of his followers also, have so often asserted. It is only a 
sieve, which decides which is to live, and what is to die. But evo- 
lutionary lines are of great length, and the evolution of a flower, or 
of an insectivorous plant is a way with many side-paths. It is the 
sieve that keeps evolution on the main line, killing all, or nearly 
all that try to go in other directions. By this means natural selec- 
tion is the one directing cause of the broad lines of evolution. 

“Of course, with the single steps of evolution it has nothing to 
do. Only after the step has been taken, the sieve acts, eliminating 
the unfit. The problem, as to how the individual steps are brought 
about, is quite another side of the question’ (De Vries, “Species 
and Varieties,” pp. 4-7, 1905). 

The distinguished French zoologist (Professor in the University 
of Paris), Delage, leader among French morphologists and experi- 

Delage’s esti- menters, voices his position concerning Darwinism in 
mate of selection. the following concise phrases (“L’Hérédité,” 2d ed., 
Pp. 397, 1903): “La sélection naturelle est un principe admirable et 
parfaitement juste. Tout le monde est d’accord aujourd’hui sur ce 
point. Mais ot l’on n’est pas d’accord, c’est sur la limite de sa 
puissance et sur la question de savoir si elle peut engendrer des 
formes spécifiques nouvelles. Il semble bien demontrer aujourd’hui 
qu’elle ne le peut pas.” 

*“A study of the recent discussion in the Contemporary Review 
between Spencer and Weismann leads to the conclusion that neither 


DARWINISM’S PRESENT STANDING. 39% 


of these acknowledged leaders of biological thought supports his 
position upon inductive evidence. Each displays his main force 

fee ohane destructive criticism of his opponent; neither pre- 
pionship of the sents his case constructively in such a manner as to 
“unknown factors carry conviction either to his opponent or to others. In 
of evolution.” short, beneath the surface of fine controversial style 
we discern these leaders respectively maintaining as finally estab- 
lished theories which are less grounded upon fact than upon the 
logical improbabilities of rival theories. Such a conclusion is deeply 
significant; to my mind it marks a turning point in the history of 
speculation, for certainly we shall not arrest research with any 
evolution factor grounded upon logic rather than upon inductive 
demonstration. A retrograde chapter in the history of science 
would open if we should do so and should accept as established 
laws which rest so largely upon negative reasoning... . 

“The first step then towards progress is the straightforward con- 
fession of the limits of our knowledge and of our present failure 
to base either Lamarckism or neo-Darwinism as universal princi- 
ples upon induction. The second is the recognition that all our 
thinking still centres around the five working hypotheses which 
have thus far been proposed; namely, those of Buffon, Lamarck, St. 
Hilaire, Darwin, and Nageli. Modern criticism has highly differ- 
entiated, but not essentially altered these hypothetical factors since 
they were originally conceived. _Darwin’s ‘survival of the fittest’ 
we may alone regard as absolutely demonstrated as a real factor, 
without committing ourselves as to the ‘origin of fitness.’ The 
third step is to recognise that there may be an unknown factor or 
factors which will cause quite as great surprise as Darwin’s.” . . 

“The general conclusion we reach from a survey of the whole 
field is, that for Buffon’s and Lamarck’s factors we have no theory 
of heredity, while the original Darwin factor, or neo-Darwinism, 
offers an inadequate explanation of evolution. If acquired varia- 
tions are transmitted, there must be, therefore, some unknown 
principle in heredity; if they are not transmitted, there must be 
some unknown factor in evolution.” (Osborn, H. F., “The Un- 
known Factors of Evolution,” in Wood’s Holl Biological Lectures, 
pp. 79, 80, 81, 98, and 99, 18904.) 

* Davenport, C. B., “Animal Morphology in its Relation to Other 
Sciences,” Congress of Arts and Sciences, Vol. V, pp. 244-257, 1906. 
In this paper are pointed out in admirable manner the present- 
moment problems, interests, and points of view of evolution biolo- 
gists. 

* Henry de Varigny, in ‘““La Nature et La Vie,” 1905, says that for 
many adaptations “il n’y a pas a se dissimuler que, dans beaucoup 


bd 


392 DARWINISM TO-DAY. 


de cas, cette explication [of the adaptation] est purement verbale; 
nous constatons un résultat. nous l’exprimons en essayant de l’inter- 
préter ; mais le mécanisme reste obscur. . . . Dans beaucoup de cas, 
Vadaptation est un phénoméne que l’on constate sans peine mais 
qui dans l’état actuel de nos connaissances, reste sans explication” 
(p. 184 and p. 185). 

Klebs, Georg, “Willktirliche Entwicklungsanderungen bei Pflan- 
zen,’ 1903. An interesting, suggestive, and valuable account of 

Klebs’s conclu- €XPeriments, and their significance, on altering the 
sion from experi- developmental phenomena of plants. Although he is 
ments on plants: strongly opposed to any vitalistic theory which attrib- 
utes to life an independence of physico-chemical laws, Klebs does 
not accept the Darwinian explanation of adaptiveness. Darwin 
“betrachtet die Zweckmassigkeit selbst als den wesentlichsten Faktor 
der Artbildung, indem nach seiner Meinung die nattrliche Zucht- 
wahl aus der Menge der richtungslos auftretenden variationen nur 
die zweckmassigkeiten Merkmale zur Ausbildung und weiteren 
Entfaltung bringt. Daher stammt die frither so verbreitete und 
heute uns sonderbar erscheinende Meinung, dass die Deutung 
eines Merkmales als eines zweckmassigen schon als eine Erklarung 
fur sein Entstehen und seine Ausbildung angenommen wurde. Die 
Geltung der Darwin’schen Theorie muss seit den Arbeiten Nagelis, 
de Vries, u. a. jedenfalls eingeschrankt werden. Das eigentliche 
Problem der Artbildung muss, wie wir spater sehen werden in 
anderer Weise, formuliert werden” (p. 3). 

Friedlander (“‘Entdeckung eines .‘Atlantischen Palolo,’” etc., Biol. 
Centralbl., Vol. XXI, pp. 352-366, i901) refers to the Darwinian 
explanation of Zweckmdssigkeit as follows: . 

“Der ganze Darwinismus im weiteren, also auch vordarwin’schen 
Sinne der Descendenzhypothese, mit oder ohne Betonung der Selek- 

Friedlander’s tionstheorie, und samt den allseitig als fertig und 
discussion of sicher festgestellt gedachten Stammbaumen aller Or- 
adaptation. ganismen, wiirde, wenn auch alles damit sonst seine 
Richtigkeit hatte, unsere Gesamterkenntnis keineswegs in so tber- 
massigem Grade bereichern, wie man friher wahnte und vor allem 
nicht in dem Masse, als dass es sich lohnte, auf die Herstellung 
der zudem immer problematischen Stammbaume sonderliche Zeit und 
Mthe zu verwenden. Zweitens aber haben die neueren Experimental- 
forschungen Arten der Zweckmassigkeit an den Tag gebracht, welche 
aus rein logischen Griinden durch die Selektionstheorie durchaus 
nicht, auch nicht einmal scheinbar, ‘erklart’?’ werden kénnen. Nun 
ist aber doch gerade die vermeintliche ‘Erklarung’ der organischen 
Zweckmassigkeit oder sogen. ‘Anpassungsvollkommenheit’ die 
Hauptstarke des eigentlichen Darwinismus. Wie die Sache jetzt 


DARWINISM’S PRESENT STANDING. 393. 


liegt, miissten die Verteidiger des Darwinismus annehmen, dass die 
organische Zweckmiassigkeit zwei vollkommen verschiedene Wurzeln 
habe. Die eine ware die alte Darwin’sche oder darwinistische— 
da namlich, wo diese logischerweise moglich ist; obwohl ja auch 
hier die Erklarung die nicht recht befriedigende Form hat, dass 
gesagt wird, die Zweckmassigkeit rihre daher, dass die weniger 
zweckmassigen Formen ausgestorben seien. Die zweite Wurzel der 
organischen Zweckmassigkeit, wie sie sich namentlich in den Selbst- 
regulationserscheinungen aussert und zwar auch unter solchen 
Bedingungen, die in der freien Natur kaum jemals vorkommen und 
daher ftir das ‘Bestehender Art’ nicht von irgend welcher Bedeutung 
sein konnen—diese zweite Wurzel der Zweckmassigkeit ist der 
eigentliche Stein des Anstosses. Die Thatsachen sind hartnackig, 
eine darwinistische Scheinerklarung ist hier unmoglich und die an 
sich doch so ausserst interessanten Erscheinungen, sowie die ganze 
experimentelle Forschungsmethode ist bei den eigentlichen Dar- 
winisten nicht in gutem Ansehen; aus dem sehr begreiflichen Grunde, 
weil jene Thatsachen fiir die betreffende Richtung unbequem sind. 
Eine Reihe sicher festgestellter Thatsachen aus dem Gebiete der 
sogen. Selbstregulation beweist also, dass es organische Zweck- 
massigkeiten und obendrein typische Beispiele von solchen giebt, 
welche dem Darwin’schen Erklarungsschema vollkommen trotzen. 
Nun aber hat die organische Zweckmassigkeit im ganzen ein so 
einheitliches Geprage, dass ein doppelter Ursprung von vorn herein 
ausserst unwahrscheinlich ist. Hieraus folgt dann weiter, dass die 
darwinistische Betrachtungsweise in der Wirklichkeit wahrscheinlich 
auch in den Fallen nicht zutrifft, wo sie logisch wenigstens die 
Moglichkeit einer Erklarung oder Quasierklarung darzubieten 
scheint. Endlich aber sollten auch diejenigen, denen die Bedenken 
gegen die darwinistischen Schlussfolgerungen nicht recht eingehen 
wollen, nachgerade doch wenigstens das einsehen, dass der Teil der 
Biologie, der sich: allenfalls im darwinistischen Sinne behandeln 
liesse oder doch in Sinne jener Richtung nach Darwin’schen Prin- 
zipien behandelt werden kann,—dass dieser Teil nur ein kleines 
und vergleichsweise auch unwichtiges Gebiet umfasst.” 

* Jacques Loeb, in a recent address (‘‘Recent Development of 
Biology,” Congress of Arts and Sciences, Vol. V, p. 17, 1906), takes 
this attitude toward the problem of species-forming: “The theory 

Loeb’s attitnde Of heredity of Mendel and de Vries is in full har- 
toward the prob- mony with the idea of evolution. The modern idea 
lem of species- of evolution originated, as is well known, with 
forming. Lamarck, and it is the great merit of Darwin to have 
revived this idea. It is, however, remarkable that none of the 
Darwinian authors seemed to consider it necessary that the trans- 


394 DARWINISM TO-DAY. 


formation of species should be the object of direct observation. It 
is generally understood in the natural sciences either that direct 
observation should form the foundation of our conclusions or 
mathematical laws, which are derived from direct observations. This 
rule was evidently considered superfluous by those writing on the 
hypothesis of evolution. Their scientific conscience was quieted by 
the assumption that processes like that of evolution could not be 
directly observed, as they occurred too slowly, and that for this 
reason indirect observations must suffice. I believe that this lack 
of direct observation explains the polemical character of this liter- 
ature, for wherever we can base our conclusions upon direct obser- 
vations polemics become superfluous. It was, therefore, a decided 
progress when de Vries was able to show that the hereditary 
changes of forms, so-called ‘mutations,’ can be directly observed, at 
least in certain groups of organisms, and secondly, that these 
changes take place in harmony with the idea that for definite 
hereditary characteristics definite determinants, possibly in the form 
of chemical compounds, must be present in the sexual cells. It seems 
to me that the work of Mendel and de Vries and their successors 
marks the beginning of a real theory of heredity and evolution. If 
it is at all possible to produce new species artificially, I think that 
the discoveries of Mendel and de Vries must be the starting point.” 

®* Schmankewitsch, A., Zeitschr. f. wiss. Zool., Vol. XXV,>p. 103, 
1875; also Zettschr. f. wiss. Zool., Vol. XXIX, p. 429, 1877. 

* Adelung, Zool-Centralbl., Vol. VI, p. 757, 1809. (A review of 
Anikin’s paper, which is in Russian.) 

1° Kellogg, V. L. “A New Artemia, and Its uaticce s 
Science, N. S., Vol. XXIV, 504-596, 1906. 

** Klebs, G., “‘Willkiirliche Entwickelungsanderungen bei Pflan- 
zen,” 1903. 

** Tower, W. L., “Evolution in Chrysomelid Beetles of the Genus 
Leptinotarsa,” Pub. No. 48, Carnegie Institution of Washington. 

“The phenomenon of variation primarily owes its existence to the 
fact that community of descent and heredity tends to produce the 
exact counterpart of the parent organisms; the process of develop- 
ment, however, is not carried out under absolutely constant or uni- 
form conditions, but in a world wherein there exist changing environ- 
mental states in endless proximity. This results in the turning 
aside in the line of development from the parental standard, per- 
haps ever so little or only in one character; but in this we have 
deviation or variation” (p. 298). 

“In the explanation of origin of variation in organisms the only 
assumption we need make is that the original unit of organic matter 
was possessed of the attributes which characterise organic matter 


DARWINISM’S PRESENT STANDING. 395 


to-day—motion, sensation, growth, and reproduction. This assump- 
tion cannot meet with any serious objection unless we change our 
ideas and definition of organic units. Granted the existence of one 
single organic unit endowed as above, there is no reason for intro- 
ducing further complications by the explanation of phenomena 
through undemonstrable hypotheses, because the fact of variation in 
organic units can be explained solely through their existence in a 
natural world surrounded by varying conditions of existence” 
(p. 299). 

“In the third chapter, where colour characters are used as sub- 
jects, it is demonstrated that variation is directly produced by 
stimuli—that from relatively invariable parents, stimuli produce 
variable offspring; and again in the fifth chapter it is shown that 
variations arise in direct response to stimuli” (p. 300). 

“T maintain, therefore, that all organic variations are responsive 
to stimuli, and are not due to inherent tendencies or latencies, or 
the product of mystic elements” (p. 300). 

*® Montgomery, T. A., in a recent book of much interest (‘‘Anal- 
ysis of Racial Descent in Animals,” 1906),.explains clearly his belief 
in the inevitable production of variation (even that called blastogenic 
or congenital), and the influence on heredity (through this varia- 
tion) by the influences of environment. 

** Brooks, W. K., “The Foundations of Zoology,” p: 43, 1899. A 
most thoughtful and keen discussion of many of the conspicuous 
problems of “philosophical biology,’ written in lucid and epigram- 
matic style. In many ways Brooks stands at the head of American 
philosophical biologists. 





ry 





INDEX. 


Adaptation, complex and cor- 
related, not explicable by 
selection, 144; Friedlander’s 


discussion of, 392; lack of, in 
egg-laying habit of Phrygani- 
dia californica, 68; the great 
need of explaining, 380; not 
all explicable by Lamarckism, 
272 

Amphimixis, Weismann’s prin- 
ciple of, 180 

Anosia, mimicry of, by Basi- 
larchia, 49 

Anti-Darwinism, present-day, 4 


Baldwin, J. M., theory of ortho- 
plasy, 208 

Basilarchia, mimicry of Anosia 
by, 49 

Bateson, W., records of discon- 
tinuous variation, 33; sugges- 
tion that mutations are Men- 
delian recessives, 351 


Battie) os) the | parts, Roux's 
theory of, 201 
Biologists, many not satisfied 


with the selection theory, 89 

Biophor, 195 

Brown-Séquard, experiments on 
guinea pigs, 290 

Buffon, theory of ultimate 
structure of protoplasm, 216 

Bumpus, H., example of in- 
creased variability due to 
emancipation from _ selection, 
560; references to papers by, 69 

Burbank, Luther, belief in» La- 
marckism, 272; scientific as- 
pects of work of, 310 


Callosamia promethea, Mayer's 
experiments with, 120 


Carcinus, Weldon’s _ selection 
experiments on, 158 
Castle, W. S., discussion of 


mutations theory, 364 


Chance, law of, variation accord- 
ing to, 32-59 

Characters, numerous, useful 
only in highly perfected state, 
49; species, of no utility, 38 

Colour and pattern of insects, 
Piepers’ antagonism to selec- 
tion explanation of, 

Conn, H. W., discussion of the 
chances of death, 83; discus- 
sion of selective value, 182; 
statement of objection to se- 
lection, based on trivial char- 
acters, 40 

Cope, E. D., belief in ortho- 
genetic evolution, 323; claim- 
ing that natural selection can- 
not make new characters, 185; 
theory of orthogenesis, 285 

Correlation, references to papers 
on, 184 

Crab, hermit and polyp, sym- 
biosis of, 23 

ee Weldon’s experiments on, 
15 

Cunningham, J. T., criticism of 
Weldon’s experiments on 
Craps, 101 *) s-discussion Bor 
orthogenesis, 320; experiments 
on flatfishes, 296; explanation 
of secondary sexual charac- 
ters, 354; theory to explain sec- 
ondary sexual differences, 124 


Dall, W., belief in 
species-change, 330 
Darwin, C., attitude toward de- 
terminate variation, 34; basis 
of theory of sexual selection, 
112; explanation of descent, 
13; on race origin from sports, 
357; theory of sexual selec- 
tion, I11; theory of ultimate 
structure of protoplasm, 218 
Darwinism attacked, 25; attack 
on, by Dennert, 7; concilia- 


sudden 


397 


398 


tory defence of, 164; death-bed 
of, 1; defended, 129; defined, 
2, 10; not synonymous with 
organic evolution, 2, 3; pres- 
ent standing of, 374; upheld 
by Lankester, 389 

Davenport, C. B., discussion of 
mutations theory, 367 

Death-bed of Darwinism, I 

Death indiscriminate, 80 

Defence of Darwinism, 129 

Degeneration, complete, not ex- 
plicable by selection, 77, 146; 
example of progressive, not 
explicable by natural selection, 
1co; explanation of, by pan- 
mixia, 190; Lamarckian ex- 
planation of, 192; Plate’s La- 
marckian explanation of, 147; 
Tayler’s Darwinian explana- 
tion of, 147; Weismann’s dis- 
cussion of, 77 

Delage, Y., criticism of Del- 
beeuf’s law, 72; criticism of 
organic selection, 210; esti- 
mate of selection, 93, 390; ma- 
chine theory of protoplasm, 
225; theory of general varia- 
tion, 289 

Delbceuf’s law, 
cism of, 72 

Dennert, E., attack on Darwin- 
isn 7 

Descent, Darwinian explanation 
of, 13; evidences for, 17; evi- 
dences of, references, 23; his- 
tory of theory of, references, 
22; natural selection the final 
arbiter in, 374; relations to 
theology, references, 23; theo- 
ries of, 187; theory of, de- 
fineg, 11; theory of, dis- 
tinguished from theory of nat- 
ural selection, 17; theory of, 
history, of, 11; theory, given 
validity by Darwin, 12; theory, 
relation to pedagogy, 21; 
theory, relation to sociology, 
21; theory, relation to theology 
and philosophy, 20 

Determinant, 95 

DeVries, H., belief of, that 
artificial races are not fixed 
and constant forms, 87; dis- 
cussion of geologic time and 


Delage’s criti- 


PDEs 


species-forming, 54; discus- 
sion of species-forming by 
selection, 389; objection to 
selection based on linear char- 
acter of variation, 139; refer- 
ences to discussions of muta- 
tions theory by, 362; summing 
up of discussion of compari- 
son of natural and artificial 
selection, 89; theory of muta- 
tions, 337; theory of the ulti- 
mate structure of protoplasm, 
220 

Dohrn, A., principle of change 
of function, 168 

Douglass, N. G., observations 
on wall lizard, 123 

Durigen, observations 
ards, 123 


Eimer, Th., theory of ortho- 
genesis, 282, 321 

Emery, C., theory of primary 
variations, 332; theory of the 
origin of secondary sexual 
characters, 353; theory to ex- 
plain secondary sexual differ- 
ences, 124 

Evolution, defined, 10; organic, 
not synonymous with Darwin- 
ism, 2, 3; Osborn’s champion- 
ship of the unknown factors 
of, 391; the unknown factors 


of, 377 
Evolution study, prime needs. of, 


378 


on liz- 


Fischer, experiments with but- 
terflies, 206 

Fleischmann, A., opposed to evo- 
lution, 8 

Friedlander, discussion of adap- 
tation, 392 

Friedman, H., theory of the con- 
vergence of organisms, 8 


Galton, F., belief in hetero- 
genesis, 332; discussion of 
specific stability, 359; discus- 
sion of variation according to 
the law of chance, 61; law of 
regression, 71; statement of 
the law of regression, 97 

Germ-cells, theories of alate 
composition of, 268 


INDEX. 


Grinnell, Jos. study of geo- 
graphic differences in the 
chickadee, 225 

Gulick, J. T., studies of Ha- 


waiian land snails, 251; theo- 
ries of isolation influence, 249 


Haacke, W., discussion of in- 
heritance of acquired char- 
acters, 270; summary of Wag- 
ner’s theory, 253 

Haeckel, E., champion of evolu- 


tion, 130 
Hatschek, B., theory of the 
ultimate structure of proto- 


plasm, 222 

Henslow, G., experiment of sow- 
ing of wheat, 80; references to 
books antagonistic to selection, 


Heterogenesis, 326; belief in, of 
Dall, 330; Emery’s theory of, 
332; Korschinsky’s theory of, 
333; proposed by von Kol- 
liker, 330 

Hutton, F. W., 
dualism, 23 

Fivyatt,) A.» experiments on 
Planorbis, 295 


argument for 


Inheritance of acquired char- 
acters, 263; Brown-Séquard’s 
experiments, 290; Cunning- 
ham’s experiments, 296; diffi- 
culties in accepting, 207; ex- 
periments with  silkworms, 
208; Fischer’s experiments, 
296; Haacke’s discussion of, 
270; Hyatt’s experiments, 295; 
logical proof of, 382; Mont- 
gomery’s explanation of, 300 ; 
references to discussions of, 
305 . 

Insects, parthenogenetical varia- 
tion in, 58; variation in, 62 

Interbreeding, swamping favour- 
able variations, 44 

Intra-selection, Roux’s theory of, 
201) *t lates: criticism. of 
Roux’s theory of, 203 

Isolation, biologic, 243; biologic, 
example of, 243; geographic, 
studied among past animals, 
241; defined, 234; importance 
of, in species-forming, 232; 


399 


not an all-sufficient agent of 
species-forming, 242; physio- 
logical, 245 ; references to dis- 
cussions of, 253, 261; sexual, 
245; theories, 232; various 
means of effecting, 234 


Jaeckel, theory of metakinesis, 
289 
Johannsen, W., experiments 


with beans bred in pure lines, 


72 
Jordan, Karl, criticism of Ver- 
non’s theory of reproductive 
divergence, 249; on mechanical 
selection, 246 
fordante DNs 
isolation, 237 


on geographic 


Kallima, case of, explained by 
Plate, 175; over-specialisation 


of, 53 
Klebs, G., experiments on plants, 


B02 na. 

Korschinsky, H., radical anti- 
selection position of, 9I; 
theory of heterogenesis, 333 

Kramer, P., classification of sec- 
ondary sexual characters, 107 


Lamarck, references to his life 
and writings, 290 

Lamarckism, 263; Burbank’s be- 
lief in, 272; favoured by Red- 
field, 305; -Plate’s discussion 
of, 273; unable to explain all 
adaptations, 272; Weismann’s. 
attack on, 266 

Lankester, R., answer to objec- 
tion to selection, based on in- 
sufficient time, 55; upholding 
of Darwinism, 389 

Law, Delbceuf’s, Delage’s criti- 
cisms of, 72; of chance, varia- 
tion according to, 32, 59; of 


regression, Galton’s, 71; of 
regression, statement of Gal- 
ton, 97 


Le Dantec, F., chemical theory 
of protoplasm, 225 
Lizards, experiments on, 123 


Loeb, J., attitude toward the 
problem of  species-forming,. 
393 


400 


Mallophaga, effects of isolation 
on, 240 

Mayer, A. G., experiments on 
Promethea, 121; experiments 
on sexual selection, 120 

Mendel, G., references to life and 
work, 356 

Mendelism, references to discus- 
sions of, 357 

Merriam, C. H., criticism of 
mutations theory, 367 

Metakinesis, Jaeckel’s theory of, 
289 

Mimicry of Anosia by Basi- 
larchia, 49 

Montgomery, Th., 
of inheritance of 
characters, 306 

Morgan, C. L., statement of con- 
ception of organic selection, 
230; theory of orthoplasy, 145, 
208; answer to objections to 
sexual selection theory, 149 

Morgan, T. H., antagonism of 
species-forming by selection, 
93; criticism of Weismann’s 
method of argument, 229; dis- 
cussion of de Vries’s theory, 
345; objections to sexual se- 
lection theory, 118; summation 
of the advantages of the muta- 
tions theory, 350 

Mutation, as used by Waagen, 
324; de Vries’s theory of, 337 

Mutations theory, American 
opinion of, 362; attitude of 
naturalists toward, 348; con- 
trasted with Lamarckism, 349; 
contrasted with the isolation 
factor, 349; discussion of, by 
Castle, 364; discussion of, by 
Davenport, 366, 367; Mer- 
riam’s criticism of, 367; Mor- 
gan’s summation of the ad- 


explanation 
acquired 


vantages: ) of,. 350°") Flate’s 
criticism of, 368; references 
to discussions of, by de 


Vries, 362 


Nageli, Ch., seven objections to 
species-forming by selection, 
62; theory of orthogenesis, 
277; theory of ultimate struct- 
ure of protoplasm, 219 


INDEX. 


Neo-Darwinians, concessions of, 


134 2o0e 
Neo-vitalism, 226 


Organisms, number of living, Io 

Orthogenesis, 274; Cope’s belief 
in, 323; Cope’s theory of, 285; 
Cunningham’s discussion of, 
326; Eimer’s theory of, 282, 
320% Nageli’s theorysotm277; 
paleontologists in favour of, 
288; Pfeffer’s theory of, 320; ~ 
Plate’s résumé of evidence for, 
279; Whitman’s declaration in 
favour of, 288 

Orthoplasy, 208; references to 
discussions of, 229 

Orthoselection, contrasted with 
orthogenesis, 276 

Osborn, H. F., championship of 
the unknown factors, of, 391; 
theory of orthoplasy, 208 


Palzontologists favouring ortho- 
genesis, 288 

Panmixia, example of ineffect- 
ive, 99; Weismann’s theory of, 
188; Wolff’s criticism of, 98 

Parallelism in variation, 279 

Parthenogenesis, variation in in- 
sects produced by, 58 

Pearson, K., discussion of varia- 
tion according to the law of 
chance, 61; theory of repro- 
ductive selection, 249 

Pedagogy, relation of, to theory 
of descent, 21 

Pfeffer, G., objection to selec- 
tion, based on the smallness of 
species-change, 75; statement 
of the fundamental difference 
between natural and artificial 
selection, 88; theory of ortho- 
genesis, 320 

Philosophy, relation to biology, 
references for, 24; relation to 
theory of descent, 20 

Phryganidia californica, lack of 
ay in egg-laying habit, 


Piepers, M. C., antagonism to 
selection explanations of 
colour and pattern in insects, 


INDEX. 


Plant-breeding, references for, 
105 

Plants, amelioration of, 
ences for, 105 

Plate, L., admission of the need 
of acquired characters to aid 
selection, 170, 178; answer to 
the claimed improbability of 
timely appearance of varia- 
tions needed in co-adaptive 
structures, 176; answer to the 
objection concerning the de- 
pendence of selection on 
chance, 170; answer to the ob- 
jection to selection based on the 
slightness of Darwinian varia- 
tions, 165; claim that correla- 
tion may aid slight variation, 
167; claim that same selective 
value may be obtained in dif- 
ferent ways, 172; claim that 
selection works with plural 
variation, 172; classification of 
secondary sexual characters 
by, 107; conciliatory defence 
of Darwinism, 164; criticism 
of mutations theory, 368; 
criticism of organic selection, 
210; criticism of Roux’s 
theory of intra-selection, 203; 
discussion of- Lamarckism, 
273; disbelief in Weismann’s 
principle of germinal selection, 
180; explanation of character 
fixity in domestic animals, 163; 
explanation of the case of 
Kallima, 175; Lamarckian ex- 
planation of degeneration, 
147; recognition of the weight 
of certain objections to Dar- 
winism, 181; résumé of facts 
tending to prove orthogene- 
sis, 279; reviewer of criticisms 
of Darwinism, 30 

Podocoryne and hermit crab, 
symbiosis of, 23 

Polyp and hermit crab,symbiosis 
of 23 

Promethea, Mayer’s experiments 
on, I21 

Protoplasm, micromeric theo- 
ries of structure of, 215; 
physical and chemical struct- 
ure of, 194; theories of ulti- 
mate structure of, 214; Weis- 


refer- 


401 


mann’s theory of the ultimate 
structure of, 195 


Quetelet, discoverer of variation 
according to the law of chance, 
61 


Redfield, C., favouring Lamarck- 
ism, 305 

Regression, Galton’s law of, 71; 
statement of Galton’s law of, 
07 

Romanes, G. J., discussion of 
Gulick’s work and conclusions, 
250; on physiological selection, 


245 
Rosa, D., theory of progressive 
reduction of variability, 322 
Roux, W., theory of intra- 
selection or battle of the parts, 
201 


Secondary sexual characters, 
Cunningham’s explanation of, 
354; Emery’s theory of the 
origin of, 353: references to 
exposition of theories, 373; 
Wallace’s suggested explana- 
tion of, 354. 

Seebohm’s criticism of physio- 
logic selection, 247 

Selection, artificial, defined, 15; 
artificial, natural selection 
resting too largely on an anal- 
ogy with, 86; based on varia- 
tion, 30; cannot explain com- 
plete degeneration, 77; co- 
efficient, Wolff’s discussion of, 
101; Darwin’s theory of sex- 
ual, 111; Delage’s estimate of, 
390; de Vries’s discussion of 
species-forming by, 389; de 
Vries’s estimate of, 93; diffi- 
culty of explaining complex 
relations among body-parts by, 
51; difficulty of explaining 
inter-species sterility by, 76; 
difficulty of explaining repeated 
identical structures by, 47; ex- 
ample of persistence of trivial 
differences in face of, 103; 
example of progressive degen- 
eration, not explicable by, 100; 
final arbiter in descent, 374; 
geologic time too short to 


402 INDEX. 


give it opportunity to do its 
work, 54; hindering rather 
than promoting species change, 
56; Korschinsky’s radical posi- 
tion against, 91; may produce 
continuous change, but not dis- 
continuous series of species, 
73; Morgan’s antagonism of 
species-forming by, 93; natu- 
ral, defined, 13; natural, needs 
sexual selection theory for 
support, 125; natural, rests too 
largely on analogy with arti- 
ficial selection, 150; needs the 
support of the sexual selection 
theory, 85; not able to explain 
complex adaptation, 144; not 
able to explain degeneration, 
146; not able to explain over- 
specialisation, 1465; not able 
to produce many-branched de- 
scent and discontinuity in 
series, 142; objection to, based 
on the linear and quantitative 
character of fluctuating varia- 
tions, 70; objections to based 
on over-specialisation, 53; per- 
sonal, how real, 82; Pfeffer’s 
objection, based on the small- 
ness of species change, 75; 
rests too largely on an analogy 
with artificial selection, 86; 


rigour of, questioned, 148; 
theories, Wigand’s criticism 
of, 387; theory of; ‘dis- 


tinguished from theory of de- 
stent, »17% 

Selection, germinal, objection to 
theory of, 200;germinal, Weis- 
mann’s ‘theory of, 188, 193; 
germinal, resulting in deter- 
minate variation, 198 

Selection, mechanical, 246 

Selection, ontogenetic, 208 

Selection, organic, 208; organic, 
Delage and Plate’s criticisms 
of, 210 


Selection, physiological, criti- 
cisms of, 247 
Selection, reproductive, Pear- 


son’s theory of, 249 
Selection, sexual, 106, 120; al- 
ternative explanations of, 124; 
answers to objections to, 148; 
criticism of, by Wolff, G., 126; 


criticism of theory of, 113; 
Darwin’s basis of theory, 112; 
defined, 16; Morgan’s objec- 
tions to, 118; other theories to 
replace theory of, 123; refer- 
ences to discussions of, 125 

Selectionists, concessions of, 90 

Sexual differences, classification 
of secondary, 107; secondary, 
106; significance of, I10 

Snodgrass, R. E., studies on bills 
of Galapagos: = birds 9 429% 
studies on biologic selection, 
245 

Sociology, relations to biology, 
references for, 24; relation to 
theory of descent, 21 

Species-forming, causes and 
means of segregation the chief 
factors in, 377; determinate 
variation<as" a” factor, 43.406 
Vries’s discussion of, by selec- 
tion, 389; Loeb’s attitude to- 
ward the problem of, 393; on 
a basis of fluctuating varia- 
tion, 35; theories of, -187; 
Tower’s experiments and con- 
clusions, 309, 304 

Spencer, H., example of the 
femur of the whale, 38; pic- 
ture of the inutility of ad- 
vantage in a single direction, 
48; theory of ultimate struct- 
ure of protoplasm, 216 

Sport in cattle, recent example 
of, 358 

Sterility, inter-species, difficulty 
of explaining by selection, 76 

Struggle for existence, actual 
rigour of, 79; defined, 13 

Symbiosis of hermit crab and 


polyp, 23. 


Tayler, J. L. answer to objec- 
tion to selection based on 
linear variation, 141; Darwin- 
ian explanation of degenera- 
tion, 147; explanation of de- 
generation by natural selec- 
tion, 162; general defence of 
natural selection, 153 

Theology, relation of, to theory 
of descent, 20 

Tower, W. L., experiments and 


INDEX. 


conclusions on species-form- 
ing, 300, 394 


Ultra-Darwinism, reaction 
against, 130 
Utility, many species characters 


of no, 38 


Variation according to the law 
of chance, 32, 59; causes of,and 
means of segregation the chief 
factors in  species-forming, 
377; determinate, apparent 
cases of, 319; determinate, as 

a species-forming factor, 33; 


determinate, produced by 
germinal selection, 108; de- 
terminate, Whitman’s _ belief 
in, 325; discontinuous, 33, 


328; favourable, swamped by 
inter-breeding, 44; fluctuating, 
yas a basis for species-forming, 
bs: fluctuating, insignificance 
Jof, 36; fluctuating, of linear 
‘and quantitative value only, 
-139; fluctuating, too slight to 
-be of selective value, 138; gen- 
-eral, Delage’s theory of, 289; 
how cumulated, 379; in in- 
sects, 62; in parthenogenetic 
insects, 58; natural selection 
_hased on, 30; necessity for co- 
“incident appearance of other, 
to make a certain one effect- 
ive, 46; non-correlated in bi- 
laterally repeated organs, 65; 
occurrence of needed coin- 
cident, 45; orthogenetic, in 
paleontology, 319; parallelism 
in, 279; references for, 57; 


suggestion concerning the 
cause of, 384 
Vejodovsky, example of pro- 


gressive degeneration not ex- 
plicable by natural selection, 
100 

Vernon, H. M., theory of repro- 
ductive divergence, 248 ; theory 
of the ultimate structure of 
protoplasm, 225 

Vestigial structures, explanation 


403 


of, by panmixia, 190; La- 

marckian explanation of, 192 
Von Kolliker, R., proposal of a 

theory of heterogenesis, 330 


Waagen, use of term mutation, 
324 

Wagner, M., formulation of 
Separations-theorte, 236; 
founder of theory of species- 
forming by geographic isola- 
tion, 234 

Wallace, A. R., criticism of Ro- 
manes’s theory, 247; suggested 
explanation of secondary 
sexual characters, 354 

Weismann, A., admission of ob- 
jections to selection, 45; at- 
tack on Lamarckism, 266; dis- 
cussion of degeneration, 77; 
principle of amphimixis, 180; 
references to evolution writ- 
ings of, 212; theory of germi- 
nal selection, 188, 193; theories 
of neo-Darwinism and _ neo- 
Lamarckism, 133; theory of 
panmixia, 188 

Weldon, selection experiments 
on Carcinus, 158 

Whitman, C. O., belief in deter- 
minate variation, 325; favour- 
ing orthogenesis, 288 

Wolff, G., attack on the assump- 
tion by selectionists of the ap- 
pearance at the right time of 
the needed variation, 64; 
criticism of panmixia by, 98; 
criticism of sexual selection, 
126; discussion of selection, co- 
efficient, 101; objections to ex- 
planation by selection of com- 
plex related body-parts, 51; 
objection to natural selection, 
based upon its dependence on 
sexual selection theory, 125; 
objections to sexual selection 
theory, 126; objection that 
selection can concern only 
quantitative changes, 70; ob- 
jection to the assumption by 
selectionists of identical and 
coincident variation, 67 





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AMERICAN INSECTS 


By VERNON L. KELLOGG 


PROFESSOR IN LELAND STANFORD, JR., UNIVERSITY 


ITH 812 figures and 11 colored plates; 647 pp. 
(Amerzcan Nature Series, Group 1); $5.00 net 
(postage 34 cents). Students’ edition, $4.00. 

comprehensive account of the natural history of the in- 
sects of America, written simply yet seriously, so as to 
be acceptable to the general reading public as well as to 
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general, or as a reference manual for authoritative in- 
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pests, special discussions of structural, physiological, or 
ecological phases of insect biology, etc. 


“Certain to be widely useful . . . readable and profusely illus- 
trated. It gives a great amount of information about the insects. 
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recommend this new product of Stanford University.”— 7. D. A. 
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‘‘Nothing needed to make this a complete guide to the study of 
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‘*Professor Kellogg’s volume will be welcomed as one of the 
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“*An excellent work, and we can heartily recommend it to all 
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‘*Kin ebenso reichhaltiges wie luxuriéds ausgestattetes Werk 
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‘*The book is of the first importance in its class.”—Out West. 


‘““This work easily ranks as the most comprehensive volume 
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amateur as well as essential to every investigator.”—&. P. felt 
tn Psyche. 


‘* We have in this single volume a whole library of insect lore.” 
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‘Es ist ein gewaltiges Unternehmen, das Verf. in diesem 
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‘The work is probably the best that exists for anyone desiring 
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HENRY HOLT AND COMPANY 


PUBLISHERS New York 


1599LJ TIP 2 


_ 16-02-87 32188 «McC Om 








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